U.S. patent number 5,969,079 [Application Number 08/327,942] was granted by the patent office on 1999-10-19 for oligomers with multiple chemically functional end caps.
This patent grant is currently assigned to The Boeing Company. Invention is credited to Hyman R. Lubowitz, Clyde H. Sheppard.
United States Patent |
5,969,079 |
Lubowitz , et al. |
October 19, 1999 |
**Please see images for:
( Certificate of Correction ) ** |
Oligomers with multiple chemically functional end caps
Abstract
Thermomechanical and thermo-oxidative stabilities in resin
composites across the range of aerospace "engineering
thermoplastic" resins are improved by forming four crosslinks at
each addition polymerization site in the backbone of the resin
using crosslinking functionalities of the general formula: ##STR1##
wherein Z= ##STR2## .beta.=the residue an organic radical selected
from the group consisting of: ##STR3## R.sub.R =a divalent organic
radical; X=halogen; Me=methyl T=allyl or methallyl. G=--CH.sub.2
--,--S--, --CO--, --SO--, --O--, --CHR.sub.3 --, or
--C(R.sub.3).sub.2 --; i=1 or 2; R.sub.3 =hydrogen, lower alkyl,
lower alkoxy, aryl, or aryloxy; and .theta.=--C.tbd.N,
--O--C.tbd.N, --S--C.tbd.N, or --CR.sub.3 .dbd.C(R.sub.3).sub.2
--
Inventors: |
Lubowitz; Hyman R. (Rolling
Hills Estates, CA), Sheppard; Clyde H. (Post Falls, ID) |
Assignee: |
The Boeing Company (Seattle,
WA)
|
Family
ID: |
46252820 |
Appl.
No.: |
08/327,942 |
Filed: |
October 21, 1994 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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773381 |
Sep 5, 1985 |
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137493 |
Dec 23, 1987 |
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167656 |
Mar 14, 1988 |
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168289 |
Mar 15, 1988 |
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176518 |
Apr 1, 1988 |
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212404 |
Jun 27, 1988 |
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241997 |
Sep 6, 1988 |
5530089 |
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460396 |
Jan 3, 1990 |
5446120 |
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619677 |
Nov 29, 1990 |
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639051 |
Jan 9, 1991 |
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043824 |
Apr 6, 1993 |
5367083 |
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079999 |
Jun 21, 1993 |
5403666 |
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159823 |
Nov 30, 1993 |
5455115 |
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161164 |
Dec 3, 1993 |
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232682 |
Apr 25, 1994 |
5516876 |
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269297 |
Jun 30, 1994 |
5550204 |
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280866 |
Jul 26, 1994 |
5512676 |
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Current U.S.
Class: |
528/170;
428/411.1; 428/473.5; 525/422; 525/432; 525/434; 525/436; 528/125;
528/128; 528/172; 528/173; 528/183; 528/188; 528/190; 528/220;
528/229; 528/272; 528/288; 528/289; 528/290; 528/310; 528/322;
528/350; 528/352; 528/353 |
Current CPC
Class: |
C08G
75/20 (20130101); C08G 75/23 (20130101); C08G
73/14 (20130101); C08G 69/44 (20130101); C08G
73/10 (20130101); C08G 73/12 (20130101); Y10T
428/31721 (20150401); Y10T 428/31504 (20150401) |
Current International
Class: |
C08G
73/10 (20060101); C08G 69/00 (20060101); C08G
73/12 (20060101); C08G 69/44 (20060101); C08G
73/14 (20060101); C08G 75/00 (20060101); C08G
73/00 (20060101); C08G 073/10 (); C08G 073/14 ();
C08G 073/12 (); C08G 069/44 () |
Field of
Search: |
;528/322,183,310,170,125,190,128,272,172,173,188,220,229,288,289,290,353,350,352
;525/432,422,434,436 ;428/411.1,473.5,474.5 |
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Primary Examiner: Seidleck; James J.
Assistant Examiner: Hampton-Hightower; P.
Attorney, Agent or Firm: Hammar; John C.
Parent Case Text
REFERENCE TO RELATED APPLICATIONS
The present application is separately a continuation-in-part
application based upon each of these seventeen, copending, United
States Patent Applications:
We incorporate these patent applications by reference.
Claims
We claim:
1. A linear or multidimensional oligomer having two or four
crosslinking sites at each end of its backbone, comprising:
##STR115## wherein Z is ##STR116## i is 1 or2 .O slashed. is
phenylene;
E is ##STR117## .O slashed. is --C.tbd.N, --O--C.tbd.N,
--S--C.tbd.N, or --CR.sub.3 =C(R.sub.3).sub.2 ;
.differential. is an organic hub;
w is 3 or4
Me is methyl;
G is --CH.sub.2 --, --C(HR.sub.3)--, --C(R.sub.3).sub.2 --, --S--,
--SO.sub.2 --, --O--, or --CO--;
R.sub.3 is lower alkyl, lower alkoxy, aryl, aryloxy or
hydrogen;
T is allyl or methallyl; and
R.sub.4 is a divalent organic radical.
2. The oligomer of claim 1 wherein R.sub.4 is an aromatic,
aliphatic, or alicyclic hydrocarbon having repeating units and, a
predominant linkage between such repeating units selected from the
group consisting of imide, imide sulfone, amideimide, ester; ether,
ether sulfone, esteramide, sulfide, amide, carbonate, cyanate
ester, of mixtures thereof.
3. The oligomer of claim 2 wherein R.sub.4 is aromatic.
4. A coreactive blend comprising the oligomer of claim 2 and a
second oligomer having a different capping site reactive with
E.
5. A blend comprising the oligomer of claim 2 and a polymer.
6. A prepreg comprising the oligomer of claim 1 and a reinforcing
additive in fiber or particulate form.
7. A multiple chemically functional ester oligomer of the formula:
##STR118## wherein P.sub.# is ##STR119## .delta. is phenylene or
pyrimidinylene; i is 1 or2;
Z is ##STR120## .O slashed. is phenylene; ##STR121## .O slashed. is
--C.tbd.N, --O--C.tbd.N, --S--C.tbd.N, or --CR.sub.3
.dbd.C(R.sub.3).sub.2 ;
j is 0, 1, or 2;
G is --CH.sub.2 --, --C(HR.sub.3)--, --C(R.sub.3).sub.2 --, --S--,
--SO.sub.2 --, --O--, or --CO--;
R.sub.3 is hydrogen, lower alkyl, lower alkoxy, aryl, or
aryloxy;
Me is methyl; and
T is methallyl or allyl.
R.sub.@ is a divalent ester hydrocarbon radical formed by the
condensation of a diol with a diacid halide, wherein at least one
of the diol or diacid halide has a repeating unit of the
formula:
or
wherein L is --SO.sub.2 --, --S--, --CO--, --(CF.sub.3).sub.2 C--,
or --(CH.sub.3).sub.2 C--.
8. A composite comprising the cured oligomer of claim 1, claim 4,
or claim 5.
9. The oligomer of claim 1 wherein R.sub.4 is an imide formed by
the condensation of a dianhydride and a diamine.
10. The oligomer of claim 1 wherein R.sub.4 is an ester formed by
the condensation of a diol and a diacid or diacid halide.
11. The oligomer of claim 1 wherein R.sub.4 is an ether.
12. The oligomer of claim 1 wherein R.sub.4 is an arylene
carbonate.
13. The oligomer of claim 1 wherein R.sub.4 is a sulfide.
14. The oligomer of claim 1 wherein R.sub.4 is an amide formed by
the condensation of a diamine and a diacid halide.
15. The oligomer of claim 1 wherein R.sub.4 is an esteramide.
16. A multiple chemically functional polyimide oligomer formed by
reacting:
(a) 2 moles of an extended anhydride end cap monomer of claim
1;
(b) n+1 moles of a polyaryl diamine having terminal amino groups,
and
(c) n moles of at least one dianhydride,
wherein n is a small integer, generally less than 20.
17. A crosslinkable polyimide oligomer having the general formula:
##STR122## wherein .xi. is the residue of an extended amine end cap
monomer of the formula: ##STR123## wherein .xi. is ##STR124## i is
1 or 2; .O slashed. is phenylene; ##STR125## Me is methyl; G is
--CH.sub.2 --, --SO.sub.2 --, --CO--, --S--, --O--,
--C(HR.sub.3)--, or C(R.sub.3).sub.2 --;
.beta. is --O--.O slashed.--NH.sub.2 ;
R.sub.3 is independently any of hydrogen, lower alkyl, lower
alkoxy, aryl, or aryloxy;
.O slashed. is --C.tbd.N, --O--C.tbd.N, --S--C--.tbd.N, or
--CR.sub.3 .dbd.C(R.sub.3).sub.2 ;
X is halogen;
T is allyl or methallyl;
R.sub.8 &R*.sub.8 is a divalent organic aromatic radical,
provided that .O slashed. is not --C.tbd.N, --OCN, or --SCN, when
.beta. is --O--R*.sub.8 --OCN;
A is the residue of a dianhydride;
B is the residue of a diamine; and
m is a small integer, generally less than 20.
18. A coreactive oligomer blend comprising a mixture of a first
oligomer of the general formula:
wherein A is a hydrocarbon backbone; and
.xi. is an unsaturated hydrocarbon residue of an end cap monomer of
the formula: ##STR126## and a second oligomer of the general
formula:
wherein k is 1, 2, or 4;
B is a hydrocarbon backbone;
Z* is a hydrocarbon residue terminating in any of: ##STR127## Y is
##STR128## i is 1 or 2; E is an unsaturated organic radical being
any of: ##STR129## R.sub.1 is lower alkyl, lower alkoxy, aryl, or
aryloxy; R.sub.3 is lower alkyl, lower alkoxy, aryl, aryloxy or
hydrogen;
j is 0, 1 or 2;
G is --CH.sub.2 --, --S--, --O--, --(Me)CH--, or --(Me).sub.2
C--;
Me is methyl;
T is methallyl or allyl;
.O slashed. is --C.tbd.N, --O--C.tbd.N, --S--C.tbd.N, or --CR.sub.3
.dbd.C(R.sub.3).sub.2 ;
Z is ##STR130## .O slashed. is phenylene; .beta. is an organic
radical being any of: ##STR131## R.sub.8 and R*.sub.8 is a divalent
organic aromatic radial, provided that .O slashed. is not
--C.tbd.N, --OCN, or --SCN, when .beta. is --O--R*.sub.8 --OCN.
19. A linear polyamideimide oligomer, comprising a compound of the
general formula:
wherein A is a divalent radical including at least one segment
selected from the group consisting of: ##STR132## .xi. is a residue
of an extended amine end cap monomer of the formula: ##STR133## Z
is ##STR134## i is 1 or 2; .O slashed. is phenylene; ##STR135## Me
is methyl; G is --CH.sub.2 --, --SO.sub.2 --, --CO--, --S--, --O--,
--C(HR.sub.3)--, or --C(R.sub.3).sub.2 --;
.beta. is --O--.O slashed.--NH.sub.2 or --O--.O slashed.--COX;
R.sub.3 is independently any of hydrogen, lower alkyl, lower
alkoxy, aryl, or aryloxy;
.O slashed. is --C.tbd.N, --O--C.tbd.N, --S--C.tbd.N, or --CR.sub.3
.dbd.C(R.sub.3).sub.2 ;
X is halogen;
T is allyl or methallyl;
R*.sub.8 are a divalent organic aromatic radical;
R.sub.2 is phenylene; and
R.sub.8 is the residue of a diamine.
20. The blend of claim 18 wherein A has a backbone that is from a
different chemical family from B to form a coreactive advanced
composite blend.
21. The blend of claim 18 further comprising a noncrosslinking
polymer.
22. An advanced composite blend comprising a mixture of at least
one oligomer of the general formula:
wherein t is an unsaturated hydrocarbon residue of an end cap
monomer of the formula: ##STR136## .O slashed. is phenylene;
.beta. is an organic radical being any of: ##STR137## and R.sub.8
and R*.sub.8 is a divalent organic aromatic radial, provided that
.O slashed. is not --C.tbd.N, --OCN, or --SCN, when .beta. is
--O--R*.sub.8 --OCN.
i is 1 or 2;
E is an unsaturated organic radical being any of: ##STR138##
R.sub.1 is lower alkyl, lower alkoxy, aryl, or aryloxy; R.sub.3 is
lower alkyl, lower alkoxy, aryl, aryloxy or hydrogen,
j is 0, 1or2;
G is --CH.sub.2 --, --S--, --O--, --(Me)CH--, or --(Me).sub.2
C--;
Me is methyl;
T is methallyl or allyl;
.O slashed. is --C.tbd.N, --O--C.dbd.N, --S--C.tbd.N, or --CR.sub.3
.dbd.C(R.sub.3).sub.2 ; and
A is a hydrocarbon residue including an aromatic, aliphatic, or
mixed aromatic and aliphatic backbone, and at least one compatible
polymer from a different chemical family than the oligomer.
23. The blend of claim 22 wherein the oligomer and polymer are
selected front the following table of oligomer/polymer pairs:
24. An advanced composite blend comprising a mixture of at least
one linear or multidimensional crosslinkable oligomer having at
least four unsaturated hydrocarbon functionalities at each end of a
linear backbone or of a multidimensional arm and at least one
noncrosslinking polymer, wherein, prior to curing, the oligomer has
an average formula weight less than that of the polymer.
25. A crosslinkable oligomer having the general formula: ##STR139##
wherein .xi. is a residue of an extended amine end cap of the
formula:
.delta. is phenylene or pyrimidinylene;
i is 1 or2;
Z is ##STR140## E is ##STR141## .O slashed. is --C.tbd.N,
--O--C.tbd.N, --S--C.tbd.N, or --CR.sub.3 .dbd.C(R.sub.3).sub.2
;
j is 0, 1, or 2;
G is --CH.sub.2 --, --SO.sub.2 --, --CO--, --S--, --O--,
--C(HR.sub.3)--, or --C(R.sub.3).sub.2 --;
R.sub.3 is hydrogen, lower alkyl, lower alkoxy, aryl, or
aryloxy
Me is methyl;
T is methallyl or allyl;
w is 3 or4
.differential. is an organic hub of valency "w";
A is the residue of a dianhydride; and
B is the residue of a diamine.
26. A process for making multiple chemically functional oligomer
suitable for making advanced composites exhibiting thermomechanical
and thermo-oxidative stability, wherein the composite has regions
of stiff, parallel crosslinks in a thermoplastic matrix, comprising
the step of simultaneously reacting substantially stoichiometric
amounts of-a crosslinkable end cap monomer of claim 18 with monomer
reactants characteristic of the oligomeric backbone.
27. A multidimensional oligomer, comprising the condensation
product of substantially stoichiometric amounts of a polyfunctional
organic hub having "w" reactive functionalities and an end cap
monomer of claim 18 wherein w is 3 or 4.
28. A composite comprising a cured prepreg having an oligomer of
claim 1 or a blend of claim 4, 5, or 24 and a reinforcing additive
in fiber or particulate form.
29. A multiple chemically functional ether oligomer of the formula:
##STR142## wherein .delta. is phenylene or pyrimidinylene; i is 1
or 2;
Z is ##STR143## .O slashed. is phenylene; ##STR144## .O slashed. is
--C.tbd.N, --O--C.tbd.N, --S--C.tbd.N, or --CR.sub.3
.dbd.C(R.sub.3).sub.2 ;
j is 0, 1,or2;
G is --CH.sub.2 --, --C(HR.sub.3)--, --C(R.sub.3).sub.2 --, --S--,
--SO.sub.2 --, --O--, or --CO--;
R.sub.3 is hydrogen, lower alkyl, lower alkoxy, aryl, or
aryloxy;
Me is methyl; and
T is methallyl or allyl.
R.sub.e is a divalent ester hydrocarbon radical formed by the
condensation of a diol with a dihalogen or dinitro, wherein at
least one of the diol or the dihalogen/dinitro has a repeating unit
of the formula:
or
wherein L is --SO.sub.2 --, --S--, --CO--, --(CF.sub.3).sub.2 C--,
or --(CH.sub.3).sub.2 C--.
30. An ether or ester oligomer useful in forming advanced
composites that have thermal stability and high glass transition
temperatures, comprising a multidimensional compound of the general
formula:
wherein P is ##STR145## T is ##STR146## n is an integer such that
the molecular weight of the repeating --R--T segment is between
about 0-3000;
R is phenyl, biphenyl, naphthyl, or a hydrocarbon chain having
linked aromatic radicals connected with at least one
electronegative linkage selected form the group consisting of
--SO.sub.2 --, --CO--, --S--, and --(CF.sub.3).sub.2 C--,
Ar is a trivalent aromatic radical;
.xi. is phenylene or pyrimidinylene;
i is 1 or2;
Z is ##STR147## .O slashed. is --C.tbd.N, --O--C.tbd.N,
--S--C.tbd.N, or --CR.sub.3 =C(R.sub.3).sub.2 ;
j is O,1,or2;
G is --CH.sub.2 --, --C(HR.sub.3)--, --C(R.sub.3).sub.2 --, --S--,
--SO.sub.2 --, --O--, or --CO--;
R.sub.3 is hydrogen, lower alkyl, lower alkoxy, aryl, or
aryloxy;
Me is methyl; and
T is methallyl or allyl.
31. A carbonate oligomer of the formula: ##STR148## wherein R.sub.c
is a divalent organic carbonate radical or a carbonate linkage;
i is 1 or 2;
w is 3 or 4;
.delta. is phenylene or pyrimidinylene;
.differential. is a "w" valent organic radical;
w is 3 or 4 ##STR149## G is --CH.sub.2 --, --SO.sub.2 --, --CO--,
--S--, --O--, --C(HR.sub.3)--, or --C(R).sub.3 --;
T is allyl or methallyl;
Me is methyl;
R.sub.3 is lower alkyl, lower alkoxy, aryl, aryloxy, or hydrogen;
and
.O slashed. is --C.tbd.N, --O--C.tbd.N, --S--C.tbd.N, or --CR.sub.3
.dbd.C(R.sub.3).sub.2.
32. The oligomer of claim 25 wherein the diamine is selected from
the group consisting of:
2,2-bis-(4-hydroxyphenyl)-propane;
bis-(2-hydroxyphenyl)-methane;
bis-(4-hydroxyphenyl)-methane;
1,1-bis-(4-hydroxyphenyl)-ethane;
1,2-bis-(4-hydroxyphenyl)-ethane;
1,1-bis-(3-chloro-4-hydroxyphenyl)-ethane;
1,1-bis-(3,5-dimethyl-4-hydroxyphenyl)-ethane;
2,2-bis-(3-phenyl-4-hydroxyphenyl)-propane;
2. 2-bis-(4-hydroxynaphthyl)-propane
2,2-bis-(4-hydroxyphenyl)-pentane;
2,2-bis-(4-hydroxyphenyl)-hexane;
bis-(4-hydroxyphenyl)-phenylmethane;
bis-(4-hydroxyphenyl)-cyclohexylmethane;
1,2-bis-(4-hydroxyphenyl)-1,2-bis-(phenyl)-ethane;
2,2-bis-(4-hydroxyphenyl)-1-phenylpropane;
bis-(3-nitro-4-hydrophenyl)-methane;
bis-(4-hydroxy-2,6-dimethyl-3-methoxyphenyl)-methane;
2,2-bis-(3,5-dichloro-4-hydroxyphenyl)-propane;
2,2-bis-(3-bromo-4-hydroxyphenyl)-propane.
Description
TECHNICAL FIELD
The present invention relates to linear and multidimensional
oligomers that include multiple chemically functional crosslinking
end cap (terminal) groups, and, preferably, to oligomers that have
four crosslinking functionalities at each end of its linear
backbone or each multidimensional arm. We call these products
"multifunctional oligomers." Composites made from these oligomers
generally have improved toughness, thermomechanical stability, and
thermo-oxidative stability because of the higher number of
crosslinks that form upon curing. They constitute engineering
thermoplastics. Blends are prepared from mixtures of the oligomers
and compatible polymers, oligomers, or both.
The present invention also relates to methods for making the
multifunctional oligomers by condensing novel end cap reactive
monomers with appropriate reactive monomers for the chains of the
respective chemical backbones, and to the multiple chemically
functional end cap monomers themselves.
BACKGROUND ART
The thermosetting resins that are commonly used today in
fiber-reinforced composites cannot be reshaped after thermoforming.
Because errors in forming cannot be corrected, these thermosetting
resins are undesirable in many applications. In addition, these
thermosetting resins, made from relatively low molecular weight
monomers, are relatively low molecular weight, and often form
brittle composites that have relatively low thermal
stabilities.
Although thermoplastic resins are well known, practical aerospace
application of high performance, fiber-reinforced thermoplastic
resins is relatively new. Fiber in such composites toughens and
stiffens the thermoplastic resin. While the industry is exploring
lower temperature thermoplastic systems, like fiber-reinforced
polyolefins or PEEKs, our focus is on high performance
thermoplastics suitable, for example, for primary structure in
advanced high speed aircraft including the High Speed Civil
Transport (HSCT). These materials should have high tensile
strength, and high glass transitions. Such materials are classified
as "engineering thermoplastics." At moderate or high temperatures,
the low performance, fiber-reinforced thermoplastic composites
(polyolefins or PEEKS, for example) lose their ability to carry
loads because the resin softens. Thus, improved thermal stability
is needed for advanced composites to find applications in many
aerospace situations. The oligomers of the present invention
produce advanced composites.
Advanced composites should be thermoplastic, solvent resistant,
tough, impact resistant, easy to process, and strong. Oligomers and
composites that have high thermomechanical stability and
thermo-oxidative stability are particularly desirable.
While epoxy-based composites like those described in U.S. Pat. No.
5,254,605 are suitable for many applications, their brittle nature
and susceptibility to degradation often force significant design
concessions when these epoxies are selected for aerospace
applications. The epoxies are inadequate for applications which
require thermally stable, tough composites, especially when the
composites are expected to survive for a long time in a hot,
oxidizing environment. Recent research has focused on polyimide
composites to achieve an acceptable balance between thermal
stability, solvent resistance, and toughness for these high
performance applications. Still the maximum temperatures for use of
the polyimide composites, such as those formed from PMR-15, can
only be used at temperatures below about 600-625.degree. F.
(315-330.degree. C.), since they have glass transition temperatures
of about 690.degree. F. (365.degree. C.). PMR composites are usable
in long term service (50,000 hours) at about 350.degree. F.
(170.degree. C.). They can withstand temperatures up to about
600.degree. F. (315.degree. C.) for up to about five hundred
hours.
PMR-15 prepregs, however, suffer significant processing limitations
that hinder their adoption because the prepreg has a mixture of the
unreacted monomer reactants on the fiber-reinforcing fabric, making
them sensitive to changes in temperature, moisture, and other
storage conditions, which cause the prepregs to be at different
stages of cure. The resulting composites have varying, often
unpredictable properties. Aging these PMR prepregs even in
controlled environments can lead to problems. The reactants on the
prepreg are slowed in their reaction by keeping them cold, but the
quality of the prepreg depends on its absolute age and on its prior
storage and handling history. And, the quality of the composite is
directly proportional to the quality of the prepregs. In addition,
the PMR monomers are toxic or hazardous (especially MDA),
presenting health and safety concerns for the workforce. Achieving
complete formation of stable imide rings in the PMR composites
remains an issue. These and other problems plague PMR-15
composites.
The commercial long chain polyimides also present significant
processing problems. AVIMID-N and AVIMID-KIII (trademarks of E. I.
duPont de Nemours) resins and prepregs differ from PMRs because
they do not include aliphatic chain terminators which the PMRs use
to control molecular weight and to retain solubility of the PMR
intermediates during consolidation and cure. Lacking the chain
terminators, the AVIMIDs can chain extend to appreciable molecular
weights. To achieve these molecular weights, however, the AVIMIDs
(and their LARC cousins) rely on the melting of crystalline powders
to retain solubility or, at least, to permit processing. It has
proven difficult to use the AVIMIDs in aerospace parts both because
of their crystalline melt intermediate stage and the PMR plague
that these AVIMID prepregs also suffer aging.
So, research continues and is now turning toward soluble systems
like those we described in our earlier patents, including
acetylenic-terminated AVIMID-KIII prepregs of the Hergenrother
(NASA-Langley) type. For these soluble systems, many different
polyimide sulfone compounds have been synthesized to provide unique
properties or combinations of properties. For example, Kwiatkowski
and Brode (U.S. Pat. No. 3,839,287) synthesized monofunctional,
maleic-capped linear polyarylimides. Holub and Evans (U.S. Pat. No.
3,729,446) synthesized similar maleic or nadic-capped,
imido-substituted polyester compositions.
For imides and many other resin backbones we have shown
surprisingly high glass transition temperatures, reasonable
processing parameters and constraints for the prepregs, and
desirable physical properties for the composites by using soluble
oligomers having difunctional caps, especially those with nadic
caps. Linear oligomers of this type include two crosslinking
functionalities at each end of the resin chain to promote
crosslinking upon curing. Linear oligomers are "monofunctional"
when they have one crosslinking functionality at each end. The
preferred oligomers from our earlier research were "difunctional,"
because they had two functional groups at each end. Upon curing,
the crosslinking functionalities provide sites for chain extension.
Because the crosslinks were generally the weakest portions of the
resulting composite, we improved thermo-oxidative stability of the
composites by including two crosslinks at each junction. We built
in redundancy, then, at each weak point. We maintained solubility
of the reactants and resins using, primarily, phenoxyphenyl sulfone
chemistries. Our work during the past fifteen years across a broad
range of resin types or chemical families is described in the
following, forty-nine United States Patents (all of which we
incorporate by reference):
______________________________________ INVENTOR PATENT TITLE ISSUE
DATE ______________________________________ Lubowitz et al.
4,414,269 Solvent Resistant November 8, 1983 Polysulfone and Poly-
ethersulfone Com- posites Lubowitz et al. 4,476,184 Thermally
Stable October 9, 1984 Polysulfone Composi- tions for Composite
Structures Lubowitz et al. 4,536,559 Thermally Stable August 20,
1985 Polyimide Polysulfone Compositions for Composite Structures
Lubowitz et al. 4,547,553 Polybutadiene October 15, 1985 Modified
Polyester Compositions Lubowitz et al. 4,584,364 Phenolic-Capped
April 22, 1986 Imide Sulfone Resins Lubowitz et al. 4,661,604
Monofunctional Cross- April 28, 1987 linking Imidophenols Lubowitz
et al. 4,684,714 Method for Making August 4, 1987 Polyimide
Oligomers Lubowitz et al. 4,739,030 Difunctional End-Cap April 19,
1988 Monomers Lubowitz et al. 4,847,333 Blended Polyamide July 11,
1989 Oligomers Lubowitz et al. 4,851,495 Polyetherimide July 25,
1989 Oligomers Lubowitz et al. 4,851,501 Polyethersulfone July 25,
1989 Prepregs, Composites, and Blends Lubowitz et al. 4,868,270
Heterocycle Sulfone September 19, 1989 Oligomers and Blends
Lubowitz et al. 4,871,475 Method for Making October 3, 1989
Polysulfone and Polyethersulfone Oligomers Lubowitz et al.
4,876,328 Polyamide Oligomers October 24, 1989 Lubowitz et al.
4,935,523 Crosslinking June 19, 1990 Imidophenylamines Lubowitz et
al. 4,958,031 Crosslinking September 18, 1990 Nitromonomers
Lubowitz et al. 4,965,336 High Performance October 23, 1990
Heterocycle Oligomers and Blends Lubowitz et al. 4,980,481
Pyrimidine-Based December 25, 1990 End-Cap Monomers and Oligomers
Lubowitz et al. 4,981,922 Blended Etherimide January 1, 1991
Oligomers Lubowitz et al. 4,985,568 Method of Making January 15,
1991 Crosslinking Imidophenyl-amines Lubowitz et al. 4,990,624
Intermediate February 5, 1991 Anhydrides Useful for Synthesizing
Etherimides Lubowitz et al. 5,011,905 Polyimide Oligomers April 30,
1991 and Blends Lubowitz et al. 5,066,541 Multidimensional November
19, 1991 Heterocycle Sulfone Oligomers Lubowitz et al. 5,071,941
Multidimensional December 10, 1991 Ether Sulfone Oligomers Lubowitz
et al. 5,175,233 Multidimensional December 29, 1992 Ester or Ether
Oligomers with Pyrimidinyl End Caps Lubowitz et al. 5,082,905
Blended Heterocycles January 21, 1992 Lubowitz et al. 5,087,701
Phthalimide Acid February 11, 1992 Halides Lubowitz et al.
5,104,967 Amideimide Oli- April 14, 1992 gomers and Blends Lubowitz
et al. 5,109,105 Polyamides April 28, 1992 Lubowitz et al.
5,112,939 Oligomers Having May 12, 1992 Pyrimidinyl End Caps
Lubowitz et al. 5,115,087 Coreactive Imido May 19, 1992 Oligomer
Blends Lubowitz et al. 5,116,935 High Performance May 26, 1992
Modified Cyanate Oligomers and Blends Lubowitz et al. 5,120,819
High Performance June 9, 1992 Heterocycles Lubowitz et al.
5,126,410 Advanced Heterocycle June 30, 1992 Oligomers Lubowitz et
al. 5,144,000 Method for Forming September 1, 1992 Crosslinking
Oligomers Lubowitz et al. 5,151,487 Method of Preparing a September
29, 1992 Crosslinking Oligomer Lubowitz et al. 5,155,206 Amideimide
Oli- October 13, 1992 gomers, Blends and Sizings for Carbon Fiber
Composites Lubowitz et al. 5,159,055 Coreactive Oligomer October
27, 1992 Blends Lubowitz et al. 5,175,234 Lightly-Crosslinked
December 29, 1992 Polyimides Lubowitz et al. 5,175,304 Halo- or
Nitro- December 29, 1992 Intermediates Useful for Synthesizing
Etherimides Lubowitz et al. 5,198,526 Heterocycle Oligomers March
30, 1993 with Multidimensional Morphology Lubowitz et al. 5,210,213
Multidimensional May 11, 1993 Crosslinkable Oligomers Lubowitz et
al. 5,216,117 Amideimide Blends June 1, 1993 Lubowitz et al.
5,227,461 Extended Difunctional July 13, 1993 End-Cap Monomers
Lubowitz et al. 5,239,046 Amideimide Sizing August 24, 1993 For
Carbon Fiber Lubowitz et al. 5,268,519 Lightly Crosslinked December
7, 1993 Etherimide Oligomers
Lubowitz et al. 5,286,811 Blended Polyimide February 15, 1994
Oligomers and Method of Curing Polyimides Lubowitz et al. 5,344,894
Polyimide Oligomers September 6, 1994 and Blends
______________________________________
The heterocycles (i.e., oxazoles, thiazoles, or imidazoles) use a
processing principle more akin to the AVIMIDs than the
phenoxyphenyl sulfone solubility principle of our other resins. The
heterocycles have poor solubility, even with our "sulfone"
chemistries, but they at least form liquid crystals or soluble
crystals in strong acids. To produce non-crystalline (amorphous)
composites, we capitalize on the ability of our heterocycles to
melt at the same temperature range as the cure and promote
crosslinking in the melt. With relatively low molecular weight,
capped, heterocycle oligomers, we can autoclave process these
materials. Autoclave processing is a significant achievement for
these heterocycles which present to the industry, perhaps, the most
challenging problems. The polybenzoxazoles we produced, in
addition, are useful at temperatures up to about 750-775.degree. F.
(400-413.degree. C.), since they have glass transition temperatures
of about 840.degree. F. (450.degree. C.). We describe
multifunctional heterocycle and heterocycle sulfones in copending
U.S. patent application Ser. No. 08/327,180, which we incorporate
by reference.
Some aerospace applications need composites which have even higher
use temperatures than these polybenzoxazoles while maintaining
toughness, solvent resistance, ease of processing, formability,
strength, and impact resistance. Southcott et al. discuss the
problems of the prior art imide systems and the advantages of our
soluble monofunctional and difunctional nadic-capped imide systems
in the article: Southcott et al., "The development of processable,
fully imidized, polyimides for high-temperature applications," 6
High Perform. Polym., 1-12 (U.K. 1994). For these extremely
demanding requirements, our multidimensional oligomers (i.e.,
oligomers that have three or more arms extending from a central
organic hub to yield three-dimensional morphology) have superior
processing parameters over more conventional, linear oligomers that
might produce composites having these high thermal stabilities. Our
multidimensional oligomers can satisfy the thermal stability
requirements and can be processed at significantly lower
temperatures. Upon curing the end caps, the multidimensional
oligomers crosslink so that the thermal resistance of the resulting
composite is markedly increased with only a minor loss of
stiffness, matrix stress transfer (impact resistance), toughness,
elasticity, and other mechanical properties. We can achieve glass
transition temperatures above 950.degree. F. (510.degree. C.) with
composites cured from our difunctional multidimensional oligomers
(which we call "star-burst" oligomers). Of course, a full range of
use temperatures are possible by selecting the hubs (which usually
is an aromatic moiety), the backbone monomers used in the arms, end
caps, and number of crosslinking functionalities per cap.
We now believe we can achieve even better properties in advanced
composites by including an even higher number of crosslinking
functionalities than the mono- or difunctional systems of the
linear or multidimensional resins discussed in our earlier patents
or patent applications. The higher density of crosslinks provide
redundancy at those locations in the macromolecular, cured
composite which are most susceptible to thermal degradation.
SUMMARY OF THE INVENTION
The present invention provides oligomers that produce advanced
composites with high thermomechanical stability and high
thermo-oxidative stability by using four crosslinking
functionalities (i.e., unsaturated hydrocarbon moieties) at each
end of the oligomer. Upon curing, the crosslinking functionalities
on adjacent oligomers form four parallel linkages in the composite
to provide the improved stabilities. The oligomers, however, retain
the preferred properties of our difunctional oligomers with respect
to handling and processing. The composites we form from our
multiple chemically functional oligomers have even higher thermal
stabilities for comparable backbone and molecular weight and have
higher compressive strengths than our composites formed using our
mono- or difunctional oligomers. The preferred oligomers generally
have soluble, stable, fully aromatic backbones. Sulfone (--SO.sub.2
--) or other electronegative linkages ("L") selected from the group
consisting of --SO.sub.2 --, --S--, --CO--, --(CF.sub.3).sub.2 C--,
or --(CH.sub.3).sub.2 C-- in the backbones between aromatic groups
provide improved toughness for the composites and provide the
improved solubility for the oligomers that is so important to
effective processing. A typical backbone usually has repeating
units of the general formula:
wherein Ar is an aromatic radical (and preferably phenylene) and L
is an electronegative linkage as previously defined. In this
description we will refer to "L" as a sulfone. Any of the
identified electronegative groups can be substituted, however, for
--SO.sub.2 --.
The four caps at each end of the backbone of a linear oligomer or
at the end of each arm of a multidimensional oligomer provide areas
of high stiffness in the composite product. These stiff, highly
crosslinked areas are relatively lightly interspersed in a
thermoplastic matrix, yielding superior composites for aerospace
applications. Generally, highly crosslinked matrices yield high
compressive strength but the composites are brittle. Thermoplastics
are tough but have significantly lower compressive strengths. In
the present invention, the multiple chemically functional end caps
produce highly crosslinked micelles within the resin matrix
equivalent in size roughly to colloidal particles. These micelles
enhance resin interactions that are vital to achieve high
compressive strengths by, we believe, adsorbing the linear polymer
chains onto the micelle surfaces and linking multiple linear
chains. Thus, we achieve thermoplastics with high compressive
strength.
Our preferred four functional crosslinkable, thermoplastic
oligomers are formed by reacting in the appropriate stoichiometry
an end cap monomer with one or more reactants selected to form the
predominant and characteristic backbone linkage by which we
identify the nature of the resulting oligomer (i.e., ether, ester,
imide, amide, amideimide, carbonate, sulfone, etc.) in a suitable
solvent under an inert atmosphere. The soluble oligomers generally
have a weight average molecular weight (MW) of between about 5,000
and 40,000, preferably between about 5,000-15,000, and more
preferably between 10,000-15,000. We generally try to synthesize
oligomers to the highest MWs we can provided that the oligomers
remain soluble in conventional processing solvents. In these
ranges, the oligomer will have thermoplastic characteristics.
Multidimensional oligomers include an organic hub and three or more
substantially identical radiating arms, each arm terminating with a
residue of a multifunctional crosslinking end cap monomer. Suitable
hubs radicals are described in the patents we earlier incorporated
by reference with respect to our monofunctional and difunctional
oligomer research, although we prefer a 1,3,5-phenylene (i.e.,
benzenetriyl). For multiple chemically functional end caps, we
prefer linear morphology over multidimensional morphology because
linear systems are easier to prepare to have significant MW in the
backbone between the caps. Such high MW better allows the micelles
that form on crosslinking to provide their advantages to the
compressive strength.
We can also blend our linear or multidimensional oligomers as we
did with the difunctional systems. A blend might include a linear
oligomer with a comparable linear polymer, a multidimensional
oligomer with a multidimensional polymer, a linear oligomer with a
multidimensional oligomer, or the like. By "polymer," we mean a
resin that does not include the crosslinking functionalities of our
oligomers. By "oligomer," we mean any molecular weight moiety that
includes crosslinking functionalities at its ends to allow it to
react (chain-extend) to increase the effective molecular weight
when the oligomer cures to form a composite. By "crosslinking
functionality," we mean a terminating, unsaturated hydrocarbon
group that can be thermally or chemically activated when the resin
is in the melt to covalently bond to an adjacent, corresponding
moiety on another oligomer.
A blend will generally include substantially equimolar amounts of
the oligomer and a polymer. The polymer will generally have the
same backbone structure and MW as the oligomer (or it might have a
higher MW since the oligomer will chain-extend upon curing). We
prepare blends by mixing miscible solutions of the oligomers and
polymers.
The present invention relates to an advanced composite blend that
is a mixture of a crosslinkable oligomer and at least one
noncrosslinking polymer from a different chemical family. In a
preferred embodiment, the oligomer has four unsaturated hydrocarbon
functionalities at each terminus. That is, if the oligomer has
linear morphology, then the oligomer has four crosslinking
functionalities at each end of the backbone. If the oligomer has
multidimensional morphology, then the four crosslinking
functionalities are on the end of each arm. Generally, the oligomer
has an average formula weight less than the average formula weight
of the polymer prior to curing the oligomer.
Prepregs and composites are the most preferred products of the
oligomers and blends, although we can also prepare varnishes,
films, and coatings. Some oligomers are also suitable as sizings
for carbon fibers. We can also prepare PMR-analogs where reactive
monomers are prepregged. By "composite," we mean the product of
curing and consolidating the oligomers to produce high MW chains
through crosslinking, chain extension.
BEST MODE CONTEMPLATED FOR CARRYING OUT THE INVENTION
We will first discuss elements that are relatively independent of
the resin chemistries before discussing the details of the end cap
monomers and, finally, the individual resin chemistries.
1. Overriding Principles and Common Features
The weight average molecular weight (MW) of the multiple chemically
functional oligomers of the present invention should provide
thermoplastic character to the oligomer and generally should be
between 5,000 and 40,000, but preferably between about 10,000 and
35,000, and still more preferably between 15,000 and 30,000. Such
weights are usually achievable by using between 1-20 molecules of
each reactant in the backbone (with two caps, of course, for linear
systems) and often between 1-5 molecules of each reactant, as those
of ordinary skill will recognize. We seek to synthesize the highest
MW that we can which will remain soluble and easy to process. We
seek the highest MW that we can successfully synthesize repeatedly
and reliably. Within the preferred range, the oligomers are
relatively easy to process to form composites that are tough, have
impact resistance, possess superior thermomechanical properties,
and have superior thermo-oxidative stability. When oligomers having
MW less than about 5,000 are cured by crosslinking, the
thermosetting character of the material is increased so that the
ability to thermoform the product may be drastically reduced or
eliminated.
Solubility of the oligomers becomes an increasing problem as chain
length increases. Therefore, from a solubility standpoint, we
prefer shorter chains for processing, if the resulting composites
retain the desired properties. That is, the chains should be long
enough to yield thermoplastic characteristics to the composites but
short enough to keep the oligomers soluble during the reaction
sequence.
We represent the oligomers of the present invention by the
formulae: .xi.--R.sub.4 --.xi. for linear oligomers or
.differential..paren open-st.A-.xi.).sub.w for multidimensional
oligomers wherein w=3 or 4; .xi. is the residue of a multiple
chemically functional end cap monomer; .differential. is a "w"
valent, multidimensional organic hub; A is a multidimensional arm,
and R.sub.4 is a divalent, linear, aromatic, aliphatic, or
alicyclic organic radical. Preferred backbones (R.sub.4 or A) are
aromatic chains to provide the highest thermal stability where the
predominant backbone linkages are selected from the group
consisting of:
imide
amideimide
etherimide
ether
ether sulfone
arylene sulfide (PPS)
ester
ester sulfone
amide
carbonate
cyanate ester and
esteramide.
We use "linear" to mean generally in a line or in one plane and to
distinguish readily from "multidimensional" where we produce 3-D
systems. "Linear" systems are not perfectly straight, because of
carbon chemistry. "Linear" systems are the conventional morphology
for polymer chemistry resulting from "head-to-tail" condensation of
the reactants to form a chain. "Multidimensional" oligomers include
a hub from which three or more arms extend.
We seek thermally stable oligomers suitable for high temperature
advanced composites. Such oligomers generally include a high degree
of aromatic groups. The stable aromatic bond energies produce an
oligomer with outstanding thermal stability. Acceptable toughness
and impact resistance is gained through selection of the linkages
within the linear chains or in the arms of aromatic groups
radiating in our multidimensional oligomers from the central
aromatic hub. These toughening linkages are ethers, esters, and the
electronegative ("sulfone") linkages (L) selected from the group
consisting of --CO--, --SO.sub.2 --, --S--, --(CF.sub.3).sub.2 C--,
or (Me).sub.2 C, that we earlier discussed. Generally, --CO-- and
--SO.sub.2 -- groups are preferred for cost, convenience, and
performance. The group --S--S-- should be avoided, since it is too
thermally labile.
We retain processability in our oligomers by keeping them soluble
in conventional processing solvents through the inclusion of
soluble segments in their backbones. The backbones generally are
formed by condensing two monomer reactants A.sub.e and B.sub.e with
chain extension quenched with our multiple chemically functional
end cap monomers. A.sub.e is an acid monomer reactant and B.sub.e
is a base. A.sub.e and B.sub.e produce the characteristic backbone
linkage --.delta..sub.e -- for which we name the oligomer. The
linear oligomers have the general formula: ##STR4## wherein m
typically is a small integer between 0 and 20. To achieve
solubility, we prefer that at least one of A.sub.e or B.sub.e
include a soluble repeating unit of the formula:
or
wherein .O slashed.=phenylene and
Generally, the A.sub.e and B.sub.e use our phenoxyphenyl sulfone
solubility principle. By analogy, we include the same principles in
our multidimensional oligomers.
In multidimensional oligomers of all resin types, the organic hub
(.differential.) includes a plurality of rays or spokes radiating
from the hub in the nature of a star to provide multidimensional
crosslinking through suitable terminal groups with a greater number
(i.e. higher density) of crosslinking bonds than linear arrays
provide. Usually the hub will have three radiating chains to form a
"Y" pattern. In some cases, we use four chains. Including more
chains may lead to steric hindrance as the hub is too small to
accommodate the radiating chains. We prefer a trisubstituted phenyl
hub (i.e., a benzenetriyl) with the chains being symmetrically
placed about the hub.
Although the preferred aromatic moieties are aryl groups (such as
phenylene, biphenylene, and naphthylene), other aromatic groups can
be used, if desired, since the stabilized aromatic bonds will also
probably provide the desired thermal stability. For example, we can
use azaline (melamine) ##STR5##
We make prepregs from the oligomers of the present invention by the
conventional method of impregnating a suitable fabric or other
reinforcement with a mixture of the oligomer and a solvent. We can
add suitable coreactants to the solvent when preparing prepregs,
especially those having maleic end caps, as taught in our earlier
patents.
We can also prepare prepregs for composites, especially for PPS
resins, by interleaving layers of fabric with layers of a resin
film comprising an oligomer or blend, and then subjecting the
resultant stack of interleaved materials to heat and pressure
sufficient to "flow" the oligomer into the fabric and to crosslink
the oligomer to form the fiber-reinforced composite. According to a
further alternative, we can spin the oligomer into fibers, and
weave these fibers with fibers of reinforcing material to produce a
prepreg. This prepreg is cured in a manner comparable to the method
of forming a composite from interleaved oligomer film and fabric
layers. Finally, especially for PPS resins, we can use the powder
impregnation technology common for prepregging PPS.
We cure the conventional prepregs by conventional vacuum bag
autoclave techniques to crosslink the end caps. Temperatures
suitable for curing are in the range of 150-650.degree. F.
(65-345.degree. C.). The resulting product is a cured, thermally
stable, solvent-resistant composite. Post-curing to ensure
essentially complete addition polymerization through the four-caps
likely is desirable if not essential. The composites have stiff,
highly crosslinked micelles dispersed in a thermoplastic matrix.
The crosslinked oligomer may also be used as an adhesive without
curing. Such adhesives may be filled, if desired.
Blended oligomers typically comprise a substantially equimolar
amount of the oligomer and a comparable polymer that is incapable
of crosslinking with the selected crosslinkable oligomers. These
blends merge the desired properties of crosslinking oligomers with
those of the noncrosslinking polymer to provide tough, yet
processable, resin blends. The comparable polymer is usually
synthesized by condensing the same monomer reactants of the
crosslinking oligomer and quenching the polymerization with a
suitable terminating group. The terminating group lacks the
hydrocarbon unsaturation common to the oligomer's end cap monomers.
In this way, the comparable polymer has the identical backbone to
that of the crosslinkable oligomer but does not have the
crosslinkable end caps. Generally the terminating group will be a
simple anhydride (such as benzoic anhydride), phenol, or benzoyl
acid chloride to quench the polymerization and to achieve a MW for
the comparable polymer substantially equal to or initially higher
than that of the crosslinkable oligomer.
We can prepare blends by combining the oligomers of the present
invention with corresponding linear or multidimensional,
monofunctional or difunctional oligomers of our earlier patents or
our copending patent applications. We can blend three or more
components. We can blend different resins (i.e., advanced composite
blends corresponding to those blends described in U.S. patent
application Ser. No. 07/619,677 or coreactive oligomer blends
corresponding to these blends described, e.g., in U.S. Pat. Nos.
5,115,087 and 5,159,055).
With blends, we can increase the impact resistance of imide
composites over the impact resistance of pure imide resin
composites without significantly reducing the solvent resistance. A
50--50 molar blend of oligomer and polymer is what we prefer and is
formed by dissolving the capped oligomer in a suitable first
solvent, dissolving the uncapped polymer in a separate portion of
the same solvent or in a second solvent miscible with the first
solvent, mixing the two solvent solutions to form a lacquer, and
applying the lacquer to fabric in a conventional prepregging
process (often called "sweep out").
Although the polymer in the blend often originally has the same
length backbone (i.e., MW) as the oligomer, we can adjust the
properties of the composite formed from the blend by altering the
ratio of MWs for the polymer and oligomer. It is probably
nonessential that the oligomer and polymer have identical repeating
units, but that the oligomer and-polymer merely be compatible in
the mixed solution or lacquer prior to sweeping out the blend as a
prepreg. Of course, if the polymer and oligomer have identical
backbones, compatibility in the blend is more likely to occur.
Solvent resistance may decrease markedly if the comparable polymer
is provided in large excess to the crosslinkable oligomer in the
blend.
The blends might be semi-interpenetrating networks (i.e., IPNs) of
the general type described by Egli et al. "Semi-Interpenetrating
Networks of LARC-TPI" available from NASA-Langley Research Center
or in U.S. Pat. No. 4,695,610.
We prepare prepregs of the oligomers or blends by conventional
techniques. While woven fabrics are the typical reinforcement, the
fibers can be continuous or discontinuous (in chopped or whisker
form) and may be ceramic, organic, carbon (graphite), or glass, as
suited for the desired application.
As shorthand, we may use the term "multifunctional" to describe
oligomers having four chemically functional groups in each end
cap.
Although para isomers are shown for the reactants and the oligomers
(and para isomers are preferred), other isomers of the monomer
reactants are possible. Meta-isomers may be used to enhance
solubility and to achieve melt-flow at lower temperatures, thereby
yielding more soluble oligomers with enhanced processing
characteristics. The isomers (para- and meta-) may be mixed.
Substituents may create steric hindrance problems in synthesizing
the oligomers or in crosslinking the oligomers into the final
composites, but substituents can be used if these problems can be
avoided.
Therefore, each aryl group for the monomer reactants may include
substituents for the replaceable hydrogens, the substituents being
selected from the group consisting of halogen, alkyl groups having
1-4 carbon atoms, and alkoxy groups having 1-4 carbon atoms. We
prefer having no substituents.
Our oligomers and blends are heat-curable resin systems. By the
term "heat-curable resin system" we mean a composition containing
reactive monomers, oligomers, and/or prepolymers which will cure at
a suitably elevated temperature to an infusible solid, and which
composition contains not only the aforementioned monomers,
oligomers, etc., but also such necessary and optional ingredients
such as catalysts, co-monomers, rheology control agents, wetting
agents, tackifiers, tougheners, plasticizers, fillers, dyes and
pigments, and the like, but devoid of microspheres or other
"syntactic" fillers, continuous fiber reinforcement, whether woven,
non-woven (random), or unidirectional, and likewise devoid of any
carrier scrim material, whatever its nature.
By the term "syntactic foam" we mean a heat-curable resin system
which contains an appreciable volume percent of preformed hollow
beads or "microspheres." Such foams are of relatively low density,
and generally contain from 10 to about 60 weight percent of
microspheres, and have a density, upon cure, of from about 0.50
g/cm.sup.3 to about 1.1 g/cm.sup.3 and preferably have loss
tangents at 10 GHz as measured by ASTM D 2520 of 0.008 or less. The
microspheres may consist of glass, fused silica, or organic
polymer, and range in diameter from 5 to about 200 Pm, and have
densities of from about 0.1 g/cm.sup.3 to about 0.4 g/cm.sup.3 to
about 0.4 g/cm.sup.3.
By the term "matrix resin" we mean a heat-curable resin system
which comprises the major part of the continuous phase of the
impregnating resin of a continuous fiber-reinforced prepreg or
composite. Such impregnating resins may also contain other
reinforcing media, such as whiskers, microfibers, short hopped
fibers, or microspheres. Such matrix resins are used to impregnate
the primary fiber reinforcement at levels of between 10 and 70
weight percent, generally from 30 to 40 weight percent. Both
solution and/or melt impregnation techniques may be used to prepare
fiber reinforced prepregs containing such matrix resins. The matrix
resins may also be used with chopped fibers as the major fiber
reinforcement, for example, where pultrusion techniques are
involved.
If the linear or multidimensional oligomers include Schiff base or
heterocycle linkages (oxazoles, thiazoles, or imidazoles), the
composites may be conductive or semiconductive when suitably doped.
The dopants are preferably selected from compounds commonly used to
dope other polymers, namely, (1) dispersions of alkali metals (for
high activity) or (2) strong chemical oxidizers, particularly
alkali perchlorates (for lower activity). We do not recommend
arsenic compounds and elemental halogens, while active dopants, are
too dangerous for general usage.
The dopants apparently react with the oligomers or polymers to form
charge transfer complexes. N-type semiconductors result from doping
with alkali metal dispersions. P-type semiconductors result from
doping with elemental iodine or perchlorates. We recommend adding
the dopant to the oligomer or blend prior to forming the
prepreg.
While research into conductive or semiconductive polymers has been
active, the resulting compounds (mainly polyacetylenes,
polyphenylenes, and polyvinylacetylenes) are unsatisfactory for
aerospace applications because the polymers are unstable in air;
unstable at high temperatures; brittle after doping; toxic because
of the dopants; or intractable. These problems are overcome or
significantly reduced with the conductive oligomers of the present
invention.
While conventional theory holds that semiconductive polymers should
have (1) low ionization potentials, (2) long conjugation lengths,
and (3) planar backbones, there is an inherent trade-off between
conductivity, toughness, and ease of processing, if these
constraints are followed. To overcome the processing and toughness
shortcomings common with Schiff base, oxazole, imidazole, or
thiazole polymers, the oligomers of the present invention generally
include "sulfone" linkages interspersed along the backbone
providing a mechanical swivel for the rigid, conductive segments of
the arms.
Having described the common features, we next turn to the end cap
monomers that characterize the structure and performance of the
oligomers of the present invention.
2. The Multiple Chemically Functional End Cap Monomers
End cap monomers of the present invention include organic compounds
of the formula: ##STR6## wherein .O slashed.=phenylene;
##STR7##
i=1 or 2; ##STR8##
R.sub.3 =independently, any of lower alkyl, lower alkoxy, aryl,
aryloxy, or hydrogen;
G=--CH.sub.2 --, --S--, --O--, or --(Me).sub.2 C--;
T=allyl or methallyl;
Me=methyl; ##STR9##
X=halogeno, and preferably chlorine;
R=a divalent residue of a diol or nitrophenol; and
R.sub.8 =the residue of an amino/acid (preferably, phenylene).
Preferably, i=2 so that the monomers have four crosslinking
functionalities (i.e., the hydrocarbon unsaturation at the chain
end). Other organic unsaturation, however, also can be used. The
end capping functionality (E) can also be a cyanate or vinyl
selected from: ##STR10## wherein R.sub.3 =hydrogen, lower alkyl,
lower aryl, lower alkoxy, or lower aryloxy.
Ethynyl, trimethylsilylethynyl, phenylethynyl, or benzyl
cyclobutane end caps may also be used, if desired. These end caps
will probably allow curing at lower temperatures, and will probably
produced composites of lower thermal stability.
Preferred end cap monomers for forming oligomers with multiple
chemically functional oligomers are phenols having the formula:
##STR11##
--.O slashed.--=phenylene;
ROH=--.O slashed.--OH or --.O slashed.--L--.O slashed.---OH;
R.sub.1 =any of lower alkyl, lower alkoxy, aryl, substituted alkyl,
substituted aryl (including in either case hydroxyl or
halo-substituents on replaceable hydrogens), aryloxy, or
halogen;
L=--SO.sub.2 --, --CO--,--S--, --(CF.sub.3).sub.2 C--, or
--(Me).sub.2 C--;
i=1 or 2;
j=0,1, or2;
G=--CH.sub.2 --, --S--, --O--, --SO.sub.2 --, --(Me)CH--, or
--(Me).sub.2 C--; and
Me=methyl (i.e., --CH.sub.3).
Preferably, j=0, so there are no R.sub.1 substituents. Also,
preferably, i=2, so each phenol monomer has four nadic
functionalities. These phenol end cap monomers link to the backbone
with an ether or ester linkage. The nadic caps are illustrative of
the capping moieties as those skilled in the art will recognize
based in our issued patents, copending applications, and the
remainder of this specification.
The phenol monomers can be made by several mechanisms. For example,
the halide end cap ##STR12## is condensed with the diol HO--.O
slashed.--SO.sub.2 --.O slashed.--OH or HO--.O slashed.--OH to
yield the desired cap. The halide end cap is formed by condensing:
##STR13## While a 1,3,5-halodiaminobenzene is shown, and this
isomer is preferred, the 1,2,4-halodiaminobenzene isomer might also
be used.
The acid or acid halide end cap monomer can be made in a similar
way substituting, however, a diaminobenzoic acid for the
halodiaminobenzene. Again, we prefer the 1,3,5-isomer, but note
that the 2,3-, 2,4-, 2,5-, 3,4-, and 3,5-diaminobenzoic acid
isomers are known. The 1,3,5-isomer provides maximum spacing
between groups, which likely is important. An extended acid halide
monomer can be made by reacting: ##STR14## to protect the amines
(probably using the 2,4-diaminonitrobenzene isomer), extracting the
nitro functionality with HO--.O slashed.--COOH to yield: ##STR15##
saponifying the imides to recover the amines, recondensing the
amines with the acid halide described above, and, finally,
converting the carboxylic acid to the acid halide, yielding:
##STR16##
Alternatively, an acid halide end cap monomer of the formula:
##STR17## is made by condensing (Z).sub.2 --.O slashed. with a
dibasic aromatic carboxylic acid in the Friedel-Crafts
reaction.
It may also be possible to make an acid halide end cap of the
formula: ##STR18## or a corresponding phenol by condensing the
halide monomer with HO--.O slashed.--COX in the Ullmann ether
synthesis over a Cu catalyst. Here, the halide monomer should be
dripped into the diol, if making the extended phenol.
For the preparation of imides where an anhydride is an important
functionality for the end cap monomer, we extend the four
functional phenol monomer of formula (II) either with nitrophthalic
anhydride ##STR19## or phthalic anhydride acid chloride (i.e.,
trimelleitic acid halide anhydride) to form an ether or ester
analog having an active anhydride. The analog, then, has the
formula: ##STR20## wherein Q=ether or ester. We can make another
extended anhydride by condensing: ##STR21## to yield: ##STR22##
Extended anhydrides link to the backbone with an imide linkage.
For the preparation of heterocycles, esters, or other oligomers, we
can prepare another extended acid monomer by condensing
nitrobenzoic acid (or the acid halide) with the extend phenol
monomer of formula (II) to yield: ##STR23## Alternatively, we can
condensed the anhydride of formula (IV A) or (IV B) with an
amino/acid, like aminobenzoic acid, to yield: ##STR24##
self-condensation of the amino/acid needs to be avoided, so it
should be added dropwise to the anhydride. The acids can be readily
converted with SOCl.sub.2 to their acid halide (--COX) analog. The
acid or acid halide end cap monomers link to the backbone with
ester, oxazole, or imidazole linkages, for example.
We can prepare amine extended caps by reacting the halide monomer
with aminophenol to yield: ##STR25## or aminobenzoic dtu with the
extended phenol monomer (taking care to avoid self-condensation of
the amino/acid) to yield: ##STR26##
We can prepare the amine end cap monomer by converting a --COX
functionality to an amine through the acid amide in the presence of
ammonia, as described in U.S. Pat. No. 4,935,523.
The remainder of this specification will usually illustrate only
the nadic end cap monomers, but those skilled in the art will
understand that any of the other crosslinking functionalities could
substitute for the nadic group.
A pyrimidine ring can be substituted for the phenylene ring in
formula (I) to form end cap monomers analogous to those described
in our U.S. Pat. Nos. 4,980,481 and 5,227,461. The aromatic
character of the pyrimidine ring should provide substantially the
same benefits as the phenylene ring. The thermo-oxidative stability
of the resulting composites, however, might be somewhat less than
that achieved for the phenyl end cap monomers. The pyrimidine
precursors are described in U.S. Pat. Nos. 3,461,461 and 5,227,461.
The compound: ##STR27## permits halo-pyrimidine end cap monomers
for use in ether syntheses. These halo-pyrimidine caps have the
formula: ##STR28##
From these examples of extended monomers, those skilled in the art
will recognize the wide range of monomers that might be used to
introduce multifunctional capping. Furthermore, if stepwise
synthetic pathways are used, the extended caps do not necessarily
need to be separately synthesized and recovered (see, e.g., the
ether and ester syntheses which follows).
We will next discuss the principal chemical families of resins that
we can prepare using the multiple chemically functional
("multifunctional") end cap monomers. These multiple chemically
functional oligomers are analogous to the monofunctional and
difunctional oligomers described in our issued patents and
copending patent applications.
3. Imide Oligomers
We preferably prepare our imide oligomers by condensing suitable
diamines and dianhydrides with an extended anhydride end cap
monomer of formula (IV A) or (IV B) or an extended amine end cap
monomer of formula (VII) or (VIII) in a suitable solvent in an
inert atmosphere. The synthesis is comparable to the processes used
for forming our analogous difunctional or monofunctional oligomers
as described in U.S. Pat. Nos. 4,536,559; 5,011,905; and
5,175,234.
Such polyimide oligomers exhibit a stable shelf life in the prepreg
form, even at room temperature, and have acceptable handling and
processing characteristics comparable to those of K-III or PMR-15.
They also likely display shear/compression/tensile properties
comparable to or better than PMR-15, and improved toughness,
especially when reinforced with high modulus carbon fibers. The
composites are essentially fully imidized, so they are stable,
insensitive to environmental conditions, and nonhazardous.
We will discuss linear polyimides first and then their
multidimensional counterparts.
a. Linear polyimides
We achieve impact resistance and toughness in aromatic polyimides
by including "sulfone" linkages (L) between the predominant imide
linkages that characterize the backbone. The "sulfone" linkages act
as joints or swivels between the aryl groups that we use to
maximize the thermal stability. Thus, we select "sulfone" diamines
and "sulfone" dianhydrides as the preferred reactants in the
simultaneous condensation of multiple chemically functional end
caps with the diamines and dianhydrides.
Although we do not prefer imide composites that include aliphatic
segments when we use our multiple chemically functional end caps,
we can make aliphatic polyimides, particularly those which include
residues of the dianhydride MCTC. Such aliphatic residues lower the
melt temperature and allow the use of lower temperature end caps,
such as oxynadic and dimethyloxynadic (DONA). The resulting
aliphatic imide oligomers cure at lower temperatures than our
aromatic oligomers, which may be an advantage in some applications.
Generally we prefer fully aromatic backbones because the goal of
multiple chemically functional end caps, particularly four
functional caps, is to achieve the highest thermo-oxidative
stability.
Sulfone (--SO.sub.2 --) or the other electronegative linkages (L)
between aromatic groups provide improved toughness. Our preferred
imides resist chemical stress corrosion, can be thermoformed, and
are chemically stable, especially against oxidation.
i. Diamine reactants
Preferred diamines for the synthesis of imide oligomers that
include our multiple chemically functional end caps have the
formula: ##STR29## wherein R* and R' are aromatic radicals, at
least one of R* and R' being a diaryl radical wherein the aryl
rings are joined by a "sulfone" linkage (L), and t is an integer
from 0 to 27 inclusive. Preferably R* is selected from the group
consisting of --.O slashed.--D--.O slashed.-- wherein
D is an electronegative linkage selected from --SO.sub.2 --,
--(CF.sub.3).sub.2 C--, or --S-- and --.O slashed.-- is phenylene.
R' is preferably selected from the group consisting of: --.O
slashed.--, --.O slashed.--M--.O slashed.--, or --.O slashed.--.O
slashed.--
wherein M=--SO.sub.2 --, --S--, --O--, --(Me).sub.2 C--, or
--(CF.sub.3).sub.2 C--.
The diamine, however, may be any of: ##STR30## wherein R.sub.5
=--.O slashed.--q--.O slashed.--
R.sub.6 =phenylene, biphenylene, naphthylene, or --.O
slashed.--M--.O slashed.--
q=--SO.sub.2, --CO--, --S--, or --(CF.sub.3).sub.2 C--, and
preferably --SO.sub.2 -- or --CO--;
m=an integer, generally less than 5, and preferably 0 or 1; and the
other variables are as previously defined.
U.S. Pat. Nos. 4,504,632; 4,058,505; 4,576,857; 4,251,417; and
4,251,418 describe other diamines that we can use. We prefer the
aryl or polyaryl ether "sulfone" diamines previously described,
since these diamines provide high thermal stability to the
resulting oligomers and composites. We can use mixtures of
diamines, but we generally use a single diamine in each backbone so
that the resulting oligomers have reliably recurrent, predictable
structure.
Our most preferred diamines are ODA, thiodianiline,
3,3'-phenoxyphenylsulfone diamine; 4,4'-phenoxphenylsulfone
diamine; 4,4'-diaminodiphenylsulfone; 4,4'-diaminodiphenyl ether,
and methylene diamine, or mixtures thereof. We often use a 50:50
molar mixture of 3,3'-phenoxyphenylsulfonediamine and
4,4'-diaminodiphenylsulfone (available from Ciba-Geigy Corp. under
the trade designation "Eporal"). Higher temperature oligomers
within the class of preferred oligomers can be prepared using the
shorter chain diamines, particularly 4,4'-diaminodiphenylsulfone.
The best results may be achievable by replacing the sulfone linkage
--SO.sub.2 -- with a smaller linkage such as --O--, --S--, or
--CH.sub.2 --.
The diamines often contain one or more phenoxyphenylsulfone groups,
such as: ##STR31##
The molecular weights of the preferred aryl diamines described
above vary from approximately 500-10,000. We prefer lower molecular
weight diamines, because they are more readily available.
When the diamine has the formula (I), the MW of these diamines vary
from approximately 500 to about 2000. Using lower molecular weight
diamines enhances the mechanical properties of the polyimide
oligomers, each of which preferably has alternating ether "sulfone"
segments in the backbones as indicated above. A typical oligomer
will include up to about 20 to 40 diamine residues, and, generally,
about 5.
We can prepare phenoxyphenyl sulfone diamines useful in this imide
synthesis by reacting two moles of aminophenol with (n+1) moles of
an aryl radical having terminal, reactive halide functional groups
(dihalogens), such as 4,4'-dichlorodiphenyl sulfone, and n moles of
a suitable bisphenol (also known as dihydroxy aryl compounds or
diols). The bisphenol is preferably selected from the group
consisting of:
2,2-bis-(4-hydroxyphenyl)-propane (i.e., bisphenol-A);
bis-(2-hydroxyphenyl)-methane;
bis-(4-hydroxyphenyl)-methane;
1,1-bis-(4-hydroxyphenyl)-ethane;
1,2-bis-(4-hydroxyphenyl)-ethane;
1,1-bis-(3-chloro-4-hydroxyphenyl)-ethane;
1,1-bis-(3,5-dimethyl-4-hydroxyphenyl)-ethane;
2,2-bis-(3-phenyl-4-hydroxyphenyl)-propane;
2,2-bis-(4-hydroxynaphthyl)-propane
2,2-bis-(4-hydroxyphenyl)-pentane;
2,2-bis-(4-hydroxyphenyl)-hexane;
bis-(4-hydroxyphenyl)-phenylmethane;
bis-(4-hydroxyphenyl)-cyclohexylmethane;
1,2-bis-(4-hydroxyphenyl)-1,2-bis-(phenyl)-ethane;
2,2-bis-(4-hydroxyphenyl)-1-phenylpropane;
bis-(3-nitro-4-hydrophenyl)-methane;
bis-(4-hydroxy-2,6-dimethyl-3-methoxyphenyl)-methane;
2,2-bis-(3,5-dichloro-4-hydroxyphenyl)propane;
2,2-bis-(3-bromo-4-hydroxyphenyl)-propane;
or mixtures thereof, as disclosed in U.S. Pat. Nos. 3,262,914.
Again, bisphenols having aromatic character (i.e., absence of
aliphatic segments), such as bisphenol A, are preferred. Other
suitable bisphenols (which we also call "diols") include:
##STR32##
The bisphenol may also be selected from the those described in U.S.
Pat. Nos. 4,584,364; 4,661,604; 3,262,914; or 4,611,048.
The dihalogens preferably are selected from the group consisting
of: ##STR33## wherein X=halogen, preferably chlorine; and L=--S--,
--SO.sub.2 --, --CO--, --(Me).sub.2 C--, and --(CF.sub.3).sub.2
C--, and preferably --SO.sub.2 -- or --CO--.
The condensation reaction for forming these phenoxyphenyl sulfone
diamines creates diamine ethers that ordinarily include
intermediate "sulfone" linkages. The condensation generally occurs
through a phenate mechanism in the presence of K.sub.2 CO.sub.3 or
another base in a DMSO/toluene solvent. The grain size of the
K.sub.2 CO.sub.3 (s) should fall within the 100-250 ANSI mesh
range.
ii. Dianhydride reactants
The dianhydride usually is an aromatic dianhydride selected from
the group consisting of:
(a) pyromellitic dianhydride,
(b) benzophenonetetracarboxylic dianhydride (BTDA),
(c) para- and meta-dianhydrides of the general formula: ##STR34##
but may be any aromatic or aliphatic dianhydride, such as
5-(2,5-diketotetrahydrofuryl)-3-methyl-cyclohexene-1,2-dicarboxylic
anhydride (MCTC) or those disclosed in U.S. Pat. Nos. 4,504,632;
4,577,034; 4,197,397; 4,251,417; 4,251,418; or 4,251,420. We can
prepare dianhydrides by condensing 2 moles of an acid halide
anhydride (e.g., trimellitic anhydride acid chloride) of the
formula: ##STR35## wherein R.sub.2 is a C.sub.(6-13) trivalent
aromatic radical (typically phenylene) with a diamine selected from
those previously described. We can use mixtures of dianhydrides, as
we do with the EPORAL diamines. We prefer a phenoxyphenyl sulfone
dianhydride of the formula: ##STR36## particularly when the diamine
is: ##STR37## where L is previously defined.
We cure the imide oligomers or prepregs (or those counterparts for
the other backbone systems) to form composites in conventional
vacuum bag techniques. We also often post-cure these imides (or any
multiple chemically functional oligomer) as described in U.S. Pat.
No. 5,116,935 to ensure that crosslinking is substantially
complete. We can use the imide oligomers (like the counterparts we
describe for the other resins backbones) as adhesives, varnishes,
films, or coatings.
b. Multidimensional polyimides
We can prepare polyimides having multidimensional morphology by
condensing the diamines, dianhydrides, and end cap monomers with a
suitable amine hub, such as triaminobenzene. For example, we can
react triaminobenzene with the phenoxyphenyl sulfone dianhydride, a
phenoxyphenyl sulfone dimine, and either the extended anhydride end
cap monomer or an extended amine end cap monomer to produce a
multidimensional, crosslinkable polyimide. The resulting
multidimensional oligomers should have surprisingly high thermal
stabilities upon curing because of the multiple chemically
functional end caps.
i. Multidimensional amine hubs
Suitable hubs include aromatic compounds having at least three
amine functionalities. Such hubs include phenylene, naphthylene,
biphenylene, or azaline amines, (including melamine radicals) or
triazine derivatives described in U.S. Pat. No. 4,574,154 of the
general formula: ##STR38## wherein R.sub.14 is a divalent
hydrocarbon residue containing 1-12 carbon atoms (and, preferably,
ethylene). We use "azalinyl" or "azaline" to mean triazines
represented by the formula: ##STR39##
We can form another class of amine hubs by reacting the
corresponding halo-hub (such as tribromobenzene) with aminophenol
to form triamine compounds represented by the formula: ##STR40## We
can react these triamine hubs with an anhydride end cap monomer or
with suitable dianhydrides, diamines, and an extended anhydride or
an amine end cap monomer. We could also use trimellitic anhydride
as a reactant in some syntheses.
Another class of suitable amine hubs comprises amines having
extended arms. For example, we can react phloroglucinol with
p-aminophenol and 4,4'-dibromodiphenylsulfone under an inert
atmosphere at an elevated temperature to achieve an amino
terminated "star" hub of the general formula: ##STR41##
ii. Multidimensional anhydride hubs
In a manner analogous to the extended anhydride end cap monomers,
we can prepare additional hubs for these multidimensional
polyimides by reacting the corresponding hydroxy-substituted hub
(such as phloroglucinol) with nitrophthalic anhydride to form
trianhydride hubs represented by the formula: ##STR42## We can
react the trianhydride with a diamine and the extended anhydride
end cap monomer. Of course, we can condense the extended anhydride
end cap monomer directly with an amine hub to prepare a
multidimensional polyimide oligomer or can condense the extended
amine end cap monomers directly with the trianhydride.
Similarly, the hub can be an amine or anhydride derivative made
from the polyols of U.S. Pat. No. 4,709,008 that we will describe
in greater detail later in this specification.
We present the following examples to better illustrate various
features of the present invention as it relates to imides.
EXAMPLE 1
Synthesis of a phenoxyphenylsulfone diamine: ##STR43## wherein m
has an average value greater than 1. (MW 5000)
In a flask fitted with a stirrer, thermometer, Barrett trap
condenser, and a nitrogen inlet tube, we mix 8.04 g (0.074 moles)
p-aminophenol, 86.97 g (0.38 moles) bisphenol-A, 281.22 g
dimethylsulfoxide (DMSO), and 167.40 g toluene and stir. After
purging with dry nitrogen, add 67.20 g of a 50% solution of sodium
hydroxide and raise the temperature to 110-120.degree. C. Remove
the water from the toluene azeotrope, and then the toluene, until
the temperature reaches 160.degree. C. Cool the reaction mixture to
110.degree. C., and add 120 g (0.42 moles)
4,4'dichlorodiphenylsulfone as a solid. Reheat the mixture to
160.degree. C. and hold for 2 hours. After cooling to room
temperature, filter the mixture to remove sodium chloride, which
precipitates, and coagulate the product in a blender from a 2%
sodium hydroxide solution containing 1% sodium sulfite. Recover the
oligomer from the solution by washing the coagulate with 1% sodium
sulfite.
U.S. Pat. Nos. 3,839,287 and 3,988,374 disclose other methods for
preparing phenoxyphenylsulfone diamines of this general type.
EXAMPLE 2
Proposed synthesis of four functional polyimide oligomers using the
diamine of Example 1, nadic-capped extended anhydride end cap
monomers, and BTDA.
Charge a reaction flask fitted with a stirrer, condenser,
thermometer, and a dry N.sub.2 purge with a 60% slurry of the
diamine of Example 1 in NMP. In an ice bath, gradually add a 10%
solution of BDTA and an anhydride end cap monomer in NMP. After
stirring for 15 min. in the ice bath, remove the bath and stir for
2 hr. Recover the oligomer by precipitating in water and drying
with alcohol (i.e., MeOH).
Adjust the formula weight of the oligomer by adjusting the
proportions of reactants and the reaction scheme, as will be known
to those of ordinary skill in the art.
EXAMPLE 3
Synthesis of the diamine: ##STR44##
Fit a reaction flask with a stirrer, thermometer, Barrett trap
condenser, and N.sub.2 inlet tube and charged 10.91 g (0.1 moles)
of p-aminophenol, 40.43 g (0.18 moles) bisphenol A, 168.6 g DMSO,
and 79.23 g toluene. After purging with nitrogen, add 36.42 g of a
50% solution of sodium hydroxide and raise the temperature to
110-120.degree. C. to remove the water from the toluene azeotrope,
and then the toluene until the temperature reaches 160.degree. C.
Cool the reaction mixture to 110.degree. C., and add 65.22 g (0.23
moles) 4,4'dichlorodiphenylsulfone as a solid. Heat the mixture to
160.degree. C. and hold for 2 hours. After cooling to room
temperature, filter the mixture to remove sodium chloride. Form a
coagulate in a blender by adding 2% sodium hydroxide solution
containing 1% sodium sulfite. Remove the coagulate and wash it with
1% sodium sulfite.
EXAMPLE 4
Proposed synthesis of polyimide oligomers using the diamine of
Example 3, a nadic extended anhydride end cap monomer, and
BTDA.
Use the procedure followed in Example 2, except substitute a
suitable amount of the diamine of Example 3 for the diamine of
Example 1.
EXAMPLE 5
Synthesis of a diamine of Example 1 (MW 10,000).
Use the procedure of Example 1, using 2.18 g (0.02 moles) of
p-aminophenol, 49.36 g (0.216 moles) of bisphenol-A, and 64.96 g
(0.226 moles) of 4,4'-dichlorodiphenyl-sulfone.
EXAMPLE 6
Proposed synthesis of four functional polyimide oligomers using the
diamine of Example 5, the extended anhydride end cap monomer, and
phenoxyphenylsulfone dianhydride.
Follow the procedure in Example 2, substituting the diamine of
Example 5, the extended anhydride end cap monomer, and
phenoxyphenylsulfone dianhydride as the reactants.
EXAMPLE 7
Proposed preparation of composites from four functional linear
polyimides.
The oligomers obtained in any of Examples 2,4, and 6 can be
impregnated on epoxy-sized T300/graphite fabric style (Union
Carbide 35 million modulus fiber 24.times.24 weave) by first
obtaining a 10 to 40% solution of resin in NMP or another
appropriate aprotic solvent, including DMAC or DMF. The solutions
can then be coated onto the dry graphite fabric to form prepregs
with 38 wt. % resin. The prepregs can be dried to less than 1
percent volatile content, cut into 6.times.6-inch pieces, and
stacked to obtain a consolidated composite of approximately 0.080
inch. The stacks of prepregs can then be vacuum bagged and
consolidated under 100-200 psi in an autoclave heated for a
sufficient time [probably for 1-2 hours at 575-600.degree. F.
(300-315.degree. C.)] to induce cure. If dimethyl oxynadic or
oxynadic anhydride capped systems are used, the prepregs likely
would be cured for 16 hours at 400OF (210.degree. C.).
EXAMPLE 8
Proposed preparation of polyimide composites for oligomers having
four functional caps.
Prepare graphite fabric prepregs, at 36 percent resin solids, using
the resins of Example 2,4, and 6 by solvent impregnation from a
dilute NMP or another aprotic solvent solution. The graphite fabric
is spread on a release film of PEP. Sweep the prepregging solution
(having approximately 10-40 wt. % oligomer) into the fabric and
allow it to dry, repeating on alternating sides, until the desired
weight of resin is applied. The prepregs can then be dried 2 hours
at 275.degree. F. (135.degree. C.) in an air-circulating oven.
Stack seven piles of each prepreg, double-wrapped in release-coated
2-mil Kapton film, and sealed in a vacuum bag for curing. Place
each vacuum bag assembly in an autoclave and heat to about
575-600.degree. F. (300-315.degree. C.) at a rate of 1-2.degree.
F./min. (0.5-1.degree. C./min.). Upon reaching 575-600.degree. F.
(300-315.degree. C.), hold the temperature substantially constant
for about 2 hr to complete the cure. To enhance high temperature
properties, post-cure for about 4-8 hr at 600-625.degree. F.
(315-330.degree. C.).
EXAMPLE 9
Anticipated solvent resistance of four functional polyimide
composites.
Samples of the cured composites of Example 8 can be machined into
1.times.0.5-inch coupons, placed in bottles containing methylene
chloride, and observed to determine if ply separation occurs. The
composites will likely remain intact, with only slight swelling,
after immersion for up to 2 months.
c. Post-curing
In another aspect of the invention, we can improve the thermal
stability of the imide composites by post-curing the composites at
temperatures of up to approximately 625-650.degree. F.
(315-330.degree. C.). Post-curing is desirable for all resin types.
It promotes complete linking. Such post-curing treatment
advantageously raises the dynamic mechanical analysis peak (and
P-transition) of the treated composites, presumably by causing full
crosslinking of the end cap functionalities. Preferably, we carry
out the post-curing treatment of the composites at a temperature of
about 625-650.degree. F. (315-330.degree. C.) for a period of
approximately 2-4 hours, but this period may vary somewhat
depending upon the particular composite being treated.
The thermal stabilities achievable with such post-curing treatment
are significantly higher than those generally realized without the
treatment. For example, for a difunctional polyimide oligomer
having a MW of about 15,000 and prepared as previously described by
reacting a difunctional imidoaniline end cap,
4,4'-phenoxyphenylsulfone dianhydride, and a 50:50 molar mixture of
3,3'-phenoxy-phenylsulfone diamine and 4,4'-diaminodiphenylsulfone,
post-curing at a temperature of approximately 625-650.degree. F.
(315-330.degree. C.) resulted in a DMA transition temperature of
about 350.degree. F. (177.degree. C.), some 40-50.degree. F. (20
-25.degree. C.) higher than without such treatment. We believe
there will be a comparable benefit from post-curing four functional
oligomers of the present invention.
In carrying out the post-cure treatment, a prepreg is first formed
by impregnating a fabric with a polyimide oligomer. The fabric can
be any of the types previously described. We heat the prepreg at an
elevated temperature (e.g. 450.degree. F. (232.degree. C.)) and
under pressure (e.g. 100 psi) for a time sufficient to cure the
prepreg and form a composite. We then post-cure the resulting
composite at a temperature of approximately 625-650.degree. F.
(315-330.degree. C.) for a time sufficient to improve the thermal
stability. During post-curing, the remaining unreacted crosslinking
functionalities reorient and react to produce a nearly fully linked
chain.
Post-curing applies to all the resin backbones. It ensures more
complete reaction of the capping functionalities. We recommend it
for all our multifunctional oligomer systems.
The bisphenol may be in phenate form, or a corresponding sulfhydryl
can be used. Of course, can use we mixtures of bisphenols and
bisulfhydryls.
Bisphenols of the type described are commercially available. Some
may be easily synthesized by reacting a dihalogen intermediate with
bis-phenates, such as the reaction of 4,4'-dichlorophenylsulfone
with bis(disodium biphenolate). Preferred dihalogens in this
circumstance are those we discussed for forming diamines.
d. Multidimensional acid hubs
While acid hubs are not used in the imides, we describe them here
while discussing extended hubs. We can convert the triazine
derivatives described in U.S. Pat. No. 4,574,154 to acid halides by
reacting the amine functionalities with phthalic acid anhydride to
form imide linkages and terminal acid functionalities (that we
convert to acid halides). We can also use the triazine derivatives
of U.S. Pat. No. 4,617,390 (or the acid halides) as the hub for
multidimensional heterocycles.
By reacting polyol aromatic hubs, such as phloroglucinol, with
nitrobenzoic acid or nitrophthalic acid to form ether linkages and
terminal carboxylic acid functionalities, we produce acid hubs. The
nitrobenzoic acid products would have three active sites while the
nitrophthalic acid products would have six; each having the
respective formula: ##STR45## Of course we can use other
nitro/acids.
We can react extended triamine hubs of the formula: ##STR46## with
an acid anhydride (i.e., trimellitic acid anhydride) to form a
polycarboxylic acid hub of the formula: ##STR47## the hub being
characterized by an intermediate ether and imide linkage connecting
aromatic groups. We can also use thio-analogs in accordance with
U.S. Pat. No. 3,933,862.
4. Amideimide Oligomers
Polyamideimides are generally injection-moldable, amorphous,
engineering thermoplastics which absorb water (swell) when
subjected to humid environments or immersed in water. Typically
polyamideimides are described in the following patents: U.S. Pat.
No. 3,658,938; U.S. Pat. Nos. 4,628,079; 4,599,383; 4,574,144; or
3,988,344. Their thermomechanical integrity and solvent-resistance
can be greatly enhanced by capping amideimide backbones with the
four functional end cap monomers.
Classical amideimides have the characteristic repeating unit:
##STR48## in the backbone, usually obtained by reacting equimolar
amounts of trimellitic acid halide anhydride and a diamine to form
a polymer of the formula: ##STR49## wherein R* is the residue of
the diamine and m represents the polymerization factor. While we
can make amideimides of this type, and quench them to oligomers by
using an extended amine end cap monomer mixed with the diamine and
trimellitic acid halide anhydride (see Example 38), we also make
more varied amideimide oligomers.
Our oligomers can also be four functional capped homologs of the
TORLON amideimides.
a. Linear amideimides
The amideimdes of the present invention generally include linkages
of the following general nature along the backbone: ##STR50##
wherein R.sub.8 =an aromatic, aliphatic, or alicyclic radical,
and preferably a phenoxyphenyl sulfone; and
R.sub.11 =a trivalent organic radical, typically a C.sub.(6-13)
aromatic radical such as phenylene.
R.sub.8 is the residue of a diamine and, throughout the amidemide
chain, can be the same or different depending on whether we use a
single diamine or a mixture of diamines. We prepare random or block
copolymers. We can prepare an amide--amide-imide--imide linkage,
for example, by condensing 2 moles of an acid halide anhydride
(e.g., trimellitic anhydride acid halide) of the general formula:
##STR51## with a diamine of the formula: H.sub.2 N--R.sub.8
--NH.sub.2 to produce an intermediate dianhydride. The linkage is
characterized by a plane of symmetry about the R.sub.8 residue. We
can use any of the diamines described for the imides.
R.sub.11 is commonly phenylene, so that the products are classical
amideimides.
We can prepare the corresponding amideimide of the general formula:
##STR52## if we use the acid anhydride (e.g., trimellitic acid
anhydride): ##STR53## instead of the acid halide anhydride (e.g.,
trimellitic anhydride acid halide), because the imide forms before
the amide. This reaction proceeds through a dicarboxylic acid
intermediate.
We can also prepare true amideimides as our U.S. Pat. No. 5,155,206
describes. In the present invention we condense an appropriate four
functional end cap monomer with the reactants in place of the
imidoaniline or acid halide caps used in our earlier patents.
We can synthesize true amideimides of the present invention by
several schemes. To obtain repeating units of the general formula:
##STR54## we mix an acid halide anhydride, particularly trimellitic
anhydride acid chloride: ##STR55## with a diamine from those
described for the imides and with an extended amine end cap in the
ratio of n: n: 2 wherein n=an integer. The acid halide anhydride
reacts with the diamine to form an intermediate dianhydride which
will condense with the remaining diamine and the amine end cap
monomer. The reaction may be carried out in two distinct stages
under which the dianhydride is first prepared by mixing
substantially equimolar amounts (or excess diamine) of the acid
halide anhydride and diamine followed by the addition of a mixture
of the diamine and the end cap monomer. Of course, the diamine used
to form the dianhydride may differ from that used in the second
stage of the reaction, or there can be a mixture of diamines from
the outset.
We can synthesize the related amideimide having repeating units of
the general formula: ##STR56## by reacting the acid anhydride with
the diamine to form an intermediate dicarboxylic acid, which can
then react with more diamine, another diamine, or an amine end cap
monomer to complete the oligomer. Again, the reaction can be
divided into steps.
The amideimide oligomers will probably improved if the condensation
of the dianhydride/dicarboxylic acid with the diamine and end cap
monomer is done simultaneously rather than sequentially.
While the oligomers we describe use an amine end cap, we can
synthesize corresponding oligomers by using an acid halide end cap
or even an anhydride end cap, if the diamine is provided in excess.
The reaction mixture generally comprises the anhydride acid halide
(--COX) or the acid anhydride (--COOH), the end cap monomer, and
the diamine with the synthesis completed in one step.
All reactions should be conducted under an inert atmosphere.
Reducing the temperature of the reaction mixture, such as by using
an ice bath, can slow the reaction rate and can assist in
controlling the oligomeric product.
As suggested in U.S. Pat. No. 4,599,383, the diamine may be in the
form of its derivative OCN--R--NCO, if desired.
We can multifunctionally cap any amideimide described in U.S. Pat.
Nos. 4,599,383; 3,988,374; 4,628,079; 3,658,938; and 4,574,144 with
an appropriate crosslinking end cap monomer, such as the acid
halide end cap, to convert the polymers to four functional
oligomers of the present invention.
We can use a sequential or homogeneous reaction scheme to condense
the reactants with sequential synthesis preferred to avoid side
reactions. Generally we condense a dianhydride or diacid halide
(depending on whether the acid halide anhydride or simply the acid
anhydride is used) diamine, and an extended anhydride end cap
monomer of formula (II). That is, we can prepare the dianhydride or
diacid halide by the condensation of a diamine with the acid
anhydride or acid halide anhydride followed by addition of
additional diamine and the end cap to complete the synthesis. Four
functional analogs of the amideimides described in our U.S. Pat.
Nos. 5,104,967; 5,155,206; 5,216,117; and 5,239,046 can be
prepared.
b. Multidimensional amideimides
The multidimensional polyamideimide oligomers include oligomers of
the general formula: ##STR57## and other four functional,
multidimensional amideimide oligomers analogous to the
monofunctional and difunctional multidimensional amideimide
oligomers our U.S. Pat. Nos. 5,227,461; 5,104,967; or 5,155,206
describe.
Diacid halide reactants
The diacid halide (or dicarboxylic acid [i.e., dibasic acid];
general formula: XOC--R.sub.9 --COX) may include an aromatic chain
segment (i.e., R.sub.9) selected from the group consisting of:
(a) phenylene;
(b) naphthylene;
(c) biphenylene;
(d) a polyaryl "sulfone" divalent radical of the general
formula:
wherein L*=S--,--O--, --CO--,--SO.sub.2 --, (Me.sub.3).sub.2 C--,
or --(CF.sub.3).sub.2 C--,
(e) a divalent radical having conductive linkages, illustrated by
Schiff base compounds, selected from the group consisting of:
##STR58## wherein R is selected from the group consisting of:
phenylene; biphenylene; naphthylene; or a divalent radical of the
general formula: --.O slashed.--W--.O slashed.-- wherein
W=--SO.sub.2 -- or --CH.sub.2 --; and g=0-4; or
(f) a divalent radical of the general formula:
wherein R.sub.10 =a C.sub.2 to C.sub.12 divalent aliphatic,
alicyclic, or aromatic radical, and, preferably, phenylene (as
described in U.S. Pat. No. 4,556,697).
The preferred diacid halide is a dibasic carboxylic acid halide of
a divalent organic radical selected from the group consisting of:
##STR59## wherein m is an integer, generally from 1-5, and the
other variables are as previously defined.
The most preferred acid halides include: ##STR60##
We can prepare Schiff base diacid halides by the condensation of
aldehydes and aminobenzoic acid halide (or other amine/acids) in
the general reaction scheme: ##STR61## or similar syntheses.
U.S. Pat. No. 4,504,632, discloses other diacid halides that we can
use including:
adipylchloride,
malonyl chloride,
succinyl chloride,
glutaryl chloride,
pimelic acid dichloride,
suberic acid dichloride,
azelaic acid dichloride,
sebacic acid dichloride,
dodecandioic acid dichloride,
phthaloyl chloride,
isophthaloyl chloride,
terephthaloyl chloride,
1,4-naphthalene dicarboxylic acid dichloride, and
4,4'-diphenylether dicarboxylic add dichloride.
We prefer polyaryl or aryl diacid halides to achieve the highest
thermal stabilities in the resulting oligomers and composites.
Particularly preferred compounds include intermediate "sulfone"
(i.e. electronegative) linkages (i.e., "L") to improve the
toughness of the resulting oligomers.
Suitable diacid halides include compounds made by reacting
nitrobenzoic acid with a bisphenol (which might also be called a
dihydric phenol, dialcohol, or diol). The reaction is the
counterpart of that for making diamines. The bisphenol is
preferably selected from the group previously described for the
imide syntheses. We prefer bisphenols having aromatic character
(i.e., absence of aliphatic segments), such as bisphenol-A. While
we prefer bisphenol-A (because of cost and availability), we can
use the other bisphenols to add rigidity to the oligomer without
significantly increasing the average formula weight over
bisphenol-A residues, and, therefore, can increase the solvent
resistance. Random or block copolymers from using different
bisphenols are possible (here as well as with the other
backbones).
c. Amideimide sizings
A major problem encountered in improving high temperature
mechanical and physical properties of reinforced resin composites
occurs because of inadequate transfer of induced matrix stress to
the reinforcement. The matrix also helps to prevent the fiber from
buckling. Sizing is often applied to the reinforcing fibers to
protect the fibers during processing and to enhance bonding at this
interface between the fibers and the resin matrix thereby more
efficiently transferring the load and stabilizing the fiber.
Sizings are essentially very thin films of resin (less than a few
wt %) applied to the fibers. To be effective, sizings should be
relatively high MW materials that form a relatively uniform
coating. Commercially available sizings include epoxy sizings under
the trade designations UC309 and UC314 from Amoco, G or W from
Hercules, EP03 from Hoechst and high performance sizings under the
trade designations L30N, L20N, UC0121 or UC0018 from Amoco.
Commercially available sizings are unsatisfactory because they are
generally monomers or low MW materials that often only partially
coat the fibers and, as a result, minimally improve composite
properties. There is a need, therefore, for improved sizings,
especially for carbon fibers intended for high performance
composites.
We described improved sizings for carbon fibers using an amideimide
polymer or a difunctional amideimide oligomer in our U.S. Pat. Nos.
5,155,206 and 5,239,046. We can now prepare analogous four
functional amideimide sizings, although they likely would provide
little improvement over polymeric amideimide sizings since capping
between the matrix and sizing would be disorganized and incomplete
at best. The amideimide polymer, a difunctional oligomer, the four
functional oligomers of the present invention, or blends of any of
these polymers and oligomers might be used. A four functional
amideimide sizing is probably best when using a four functional
oligomer as the matrix for a sizing, the amideimide should have a
MW above 10,000, and, preferably, above 20,000. Actually, the MW
should be as high as one can achieve. As for the polymers and
difunctional oligomers, a preferred four functional amideini-de
oligomer is formed by condensing trimellitic anhydride acid
chloride with bis(4-aminophenoxyphenyl) sulfone and either an
extended amine, an acid chloride, or a phenol end cap monomer.
When the matrix is an oligomer that includes crosslinking
functionalities of the nature suggested for the capped sizings of
the present invention, it is probably wise that the caps on the
oligomer and on the sizings be the same or at least chemically
comparable. That is, for example, we prefer to use nadic caps in
our oligomers and nadic caps for the amideimide sizing.
We believe that the amideimide sizings provide a high concentration
of hydrogen bonding sites to promote coupling between the sizing
and the matrix. Both the imide and amide linkages include
heteroatoms. The capped materials may actually form chemical
(covalent) bonds for even stronger interaction between the sizing
and matrix, or the end caps might cause addition polymerization to
provide even higher MW sizings on the fiber. We believe higher MW
sizings have better properties.
The sizings impart improved elevated temperature mechanical and
environmental stability to carbon fiber/oligomer composites in
which the matrix resin is selected from imides, amides,
amideimides, esters, ethers, sulfones, ether sulfones,
heterocycles, carbonates, and almost any other commercial resin
including epoxies, PMR-15, K-III, or the like. We use these
multifunctional amideimide sizings in the same manner as
conventional sizings.
We next provide some examples of proposed syntheses of
polyamideimides.
EXAMPLE 10
React a diamine with two moles of trimellitic acid anhydride to
form a dicarboxylic acid intermediate by adding the diamine
dropwise to the trimellitic acid anhydride. Convert the
intermediate to the corresponding diacid chloride in the presence
of SOCl.sub.2, and then condense the intermediate with the diamine
and an extended amine end cap monomer to yield the desired
product.
If excess diamine is used, use an acid halide end cap to form the
product.
EXAMPLE 11
React a diamine with trimellitic anhydride acid chloride to yield a
dianhydride intermediate. Condense the intermediate with an amine
end cap monomer and a diamine to yield the desired product.
Typically, this reaction involves mixing, for example, the four
nadic-capped acid chloride end cap monomer: ##STR62## wherein NA is
nadic and .O slashed. is phenylene with trimellitic acid chloride
anhydride: ##STR63## in NMP or another suitable solvent and, then,
adding the diamine:
in NMP (i.e., the same solvent). We prepare the diamine by reacting
para- or meta-aminophenol with ##STR64##
It may be possible to obtain the amideimide in another fashion,
involving protecting the amine functionalities in the cap that
ultimately form the amide linkages with phthalic anhydride;
condensing the protected phthalic imide acid chloride end cap
monomer the diamine, and trimellitic acid chloride anhydride;
saponifying the resulting product to yield a bis(diamino) oligomer;
and completing the capping by condensing a phthalimide acid halide
end cap monomer, such as those in U.S. Pat. No. 5,087,701, and,
preferably the dinadic acid chloride monomer. Our concern with this
scheme is whether the sapionification reaction will also break the
imide linkages in the backbone.
EXAMPLE 12
Condense triaminobenzene with a trimellitic acid anhydride or acid
chloride and an amine end cap monomer to yield the desired
multidimensional product. Any amine hub can be used in place of
triaminobenzene.
EXAMPLE 13
React an amine hub with the dicarboxylic acid intermediate of
Example 15, a diamine, and an extended amine end cap in the ratio
of 1 mole of hub: (w)(m+1) moles of intermediate:(w)(m) moles of
diamine: w moles of end cap to prepare the desired multidimensional
product.
EXAMPLE 14
React an amine hub with the dianhydride intermediate of Example 11,
a diamine, and the extended amine end cap in the ratio of 1 mole
hub: (w)(m+1) moles dianhydride: (w)(m) moles diamine: w moles end
cap to yield the desired product.
EXAMPLE 15
React an acid or acid halide hub, like cyuranic acid, with a
diamine, a dicarboxylic acid intermediate of Example 10, and an
acid halide end cap in the ratio of 1 mole hub: (w)(m+1) moles
diamine: (w)(m) moles intermediate: w moles cap to yield the
desired product.
EXAMPLE 16
React an amine hub with a dicarboxylic add intermediate (or
dihalide) of Example 10 and the extended amine end cap in the ratio
of 1 mole hub: w moles intermediate: w moles cap to yield the
desired product.
EXAMPLE 17
React an amine hub with the dicarboxylic acid intermediate of
Example 10, a diamine, and an acid halide end cap in the ratio of I
mole hub: w moles intermediate w moles diamine, and w moles cap to
form the desired product.
EXAMPLE 18
React an amine hub with the dianhydride intermediate of Example 10,
a diamine, and an acid halide end cap in the ratio of I mole hub:
(w)(m) moles intermediate: (w)(m) moles diamine: w moles cap to
form the desired product.
EXAMPLE 19
React an amine hub with the dicarboxylic acid intermediate of
Example 10, a diamine, and an extended amine end cap in the ratio
of 1 mole hub: (w)(m+1) moles intermediate: (w)(m) moles diamine: w
moles cap to form the desired product.
EXAMPLE 20
React an amine hub with trimellitic anhydride acid halide, a
diamine, and an acid halide end cap in the ratio of 1 mole hub: w
moles trimellitic anhydride acid halide: w moles diamine: w moles
cap to form the desired product. Preferably the reaction occurs in
two steps with the reaction of the hub and trimellitic anhydride
acid halide followed by the addition of an amine end cap.
EXAMPLE 21
React an amine hub with trimellitic acid anhydride and an extended
amine end cap in the ratio of I mole hub: w moles trimellitic acid
anhydride: w moles cap to form the desired product.
EXAMPLE 22
React an amine hub with trimellitic acid anhydride, a diamine, and
an extended amine end cap in the ratio of 1 mole hub: 2w moles acid
anhydride: w moles diamine: w moles cap to yield the desired
product. Preferably the cap and half of the acid anhydride are
mixed to form an end cap conjugate prior to mixing the reactants to
form the oligomer. It also may be wise to mix the remaining acid
anhydride with the hub to form an acid hub conjugate prior to
adding the diamine and end cap conjugate. In an alternate synthesis
we use an anhydride end cap monomer.
Alternatively; make the product by reacting the hub with the
dianhydride intermediate of Example 11 and an extended amine end
cap.
EXAMPLE 23
React an amine hub with the dianhydride intermediate of Example 11,
a diamine, and either an extended anhydride end cap conjugate
formed by reacting an amine end cap with an acid halide anhydride
(like trimellitic acid chloride anhydride) or the anhydride end cap
monomer in the ratio of 1 mole hub: w moles intermediate: w moles
end cap conjugate.
Alternatively, prepare the product by reacting the hub with an acid
anhydride followed by reaction with a diamine, the diacid
intermediate of Example 10, and an amine end cap. Stepwise addition
of the diamine to the extended hub followed by addition of the
diacid intermediate and amine end cap will reduce competitive side
reactions.
EXAMPLE 24
React an amine hub with an acid anhydride (like trimellitic acid
anhydride) to form an acid hub intermediate. React the intermediate
with a diamine, a dicarboxylic acid or acid halide intermediate of
Example 10, and an acid halide end cap in the ratio of 1 mole hub
intermediate: (w)(m+1) moles diamine: (w)(m) moles dicarboxylic
acid intermediate: w moles end cap to yield the desired
product.
Alternatively, prepare the product by reacting an amine hub with
the dianhydride intermediate of Example 11, a first diamine, an
acid anhydride, a second diamine, and an acid halide end cap in a
stepwise reaction.
EXAMPLE 25
React an amine hub with the dianhydride intermediate of Example 11,
a diamine, and an extended amine end cap in the ratio of 1 mole
hub: 2w moles intermediate: w moles diamine: w moles cap to yield
the desired product.
EXAMPLE 26
React an acid hub with a diamine, an acid anhydride, and an amine
end cap in the ratio of 1 mole hub: w moles diamine: w moles acid
anhydride: w moles cap to yield the desired product. Preferably the
reaction includes the steps of reacting the acid anhydride with the
end cap monomer prior to addition of the hub and diamine.
EXAMPLE 27
React an acid hub with a diamine to form an amine extended hub
conjugate. React the conjugate with an acid halide anhydride, a
second diamine, and an acid halide end cap to yield the desired
product. Preparing an end cap conjugate by reacting the second
diamine with the acid halide cap (adding the cap dropwise to the
diamine) prior to the addition of the other reactants reduces side
or competitive reactions. In this case, for example, the acid hub
is added dropwise to the diamine to promote substantially complete
addition of the free amino groups with the hub's acid
functionalities and to minimize addition of a hub to both ends of
the diamine. We take similar precautions in making the other
conjugates we describe in these examples.
EXAMPLE 28
React an acid hub with a diamine, the acid intermediate of Example
10, and an extended amine end cap in the ratio of 1 mole hub: w
moles diamine: w moles intermediate: w moles cap. Preferably, the
reaction occurs in two stages with the hub being mixed with the
diamine to form an amine conjugate to which the acid or acid halide
intermediate and cap is added in a simultaneous condensation.
EXAMPLE 29
React an acid hub with a diamine, the acid intermediate of Example
10, and an extended amine cap in the ratio of 1 mole hub: (w)(m+1)
moles diamine: (w)(m) moles intermediate: w moles cap to yield the
desire product. The reaction preferably involves the step of
preparing the amine conjugate described in Example 33.
EXAMPLE 30
React two moles of an extended amine end cap with about (m+2) moles
of trimellitic acid anhydride, and about (2m+1) moles of
bis(4-aminophenoxyphenyl)sulfone:
to yield the desired product. To avoid side or competitive
reactions, prepare a dicarboxylic acid intermediate by mixing the
acid anhydride and diamine in the ratio of about 2 moles acid
anhydride: 1 mole diamine prior to adding the remaining reactants
for simultaneous condensation to the oligomer.
EXAMPLE 31
Follow the method of Example 10 except substitute aniline for the
amine cap. The product is a comparable amideimide polymer of
similar MW and structure to the oligomer of Example 10 but being
incapable of crosslinking because of the lack of crosslinking sites
(hydrocarbon unsaturation) in the end caps. The aniline provides MW
control and quenches the amideimide condensation.
We can obtain comparable noncrosslinking amideimide polymers using
the methods of Examples 11-30 substituting aniline, benzoic acid,
or similar compounds to quench the syntheses, as will be understood
by those of ordinary skill. In analogous manner, we can make
corresponding, noncrosslinking polymers for any oligomer we
describe in this specification, and we can use these polymers in
blends.
EXAMPLE 32
Mix solutions of the amideimide oligomer of Example 10 and the
amideimide polymer made in accordance with Example 31 to prepare a
blend that either can be swept out into fiber reinforcement to form
a prepreg of an amideimide blend or that can be dried to recover
the blend. The blend generally includes substantially equimolar
amounts of the oligomer and polymer, although the ratio can be
varied to control the properties of the blend.
EXAMPLE 33
Dissolve an extended amine end cap and bis(4-aminophenoxyphenyl)
sulfone in N,N'-dimethylacetamide (DMAC). Cool the solution to
-10.degree. C. under nitrogen. While stirring, add trimellitic
anhydride acid chloride dropwise and hold the temperature below
0.degree. C. one hour. Next add triethylamine (TEA) dropwise and
stir 30 minutes. Add DMAC and stir 3 more hours. Finally, add
pyridine and acetic anhydride. Stir the viscous mixture 3 hours.
Filter off the hydrochloride salt and precipitate the product in a
blender with water. Filter, wash the precipitate the product with
distilled water and then dry.
Alternatively, the imidization reaction can be induced thermally by
heating the mixture to about 300-350.degree. F. (150-175.degree.
C.) for several hours followed by precipitating the product in
water and washing with MeOH.
EXAMPLE 34
A proposed linear advanced composite blend.
Make an amideimide oligomer in accordance with Example 10.
Make a relative high MW polyether polymer by condensing a diol of
the general formula:
with Cl--.O slashed.--Cl and phenol or chlorobenzene (to quench the
polymerization) under an inert atmosphere in the same solvent as
used with the amideimide oligomer or another solvent miscible with
that of the amideimide oligomer.
Mix the two solutions to form a lacquer or varnish of an advanced
composite blend. Prepreg the lacquer or dry it prior to curing the
blend to an advanced amideimide/ether composite. This advanced
composite blend could be mixed with a Z*.sub.k --B--Z*.sub.k
oligomer to form a coreactive oligomer blend, which would, then, be
prepregged and cured. "Z*" is a cyclobutane, amine, phenol, or
thioether.
For additional discussion of advanced composite blends, see section
14. Section 15 discusses coreactive oligomer blends in more
detail.
EXAMPLE 35
A proposed multidimensional advanced composite blend.
Prepare a multidimensional, polyether sulfone polymer by reacting
phloroglucinol with Cl--.O slashed.--Cl and HO--.O slashed.--O.O
slashed.--SO.sub.2 --.O slashed.--O--.O slashed.--OH. Quench the
polymerization with either chlorobenzene or phenol. The
condensation occurs in a suitable solvent under an inert
atmosphere. The product is not recovered from the solvent.
Prepare a multidimensional, ester oligomer in the same solvent as
used for the polymer or in another miscible solvent by condensing
cyuranic acid chloride with a phenol end cap. The oligomer product
is not recovered, but the reaction mixture is mixed with the
polyether polymer product and a phenoxyphenyl sulfone diamine
(i.e., Z-B-Z, such as bis(4-aminophenoxyphenyl) sulfone) to form a
multidimensional advanced composite blend of coreactive oligomers
that can be prepregged or dried prior to curing the ester oligomer
to form a multidimensional, polyester/polyether-sulfone, advanced
composite.
Generally, in coreactive oligomer blends, the resins are selected
to tailor the physical properties of the resulting block copolymer
composites. Such blends with multiple chemically functional
oligomers are counterparts to the coreactive oligomer blends U.S.
Pat. Nos. 5,115,087 and 5,159,055 describe. For example, we can
achieve stiffening for a composite made from ethersulfone oligomer
of the present invention by adding a benzoxazole oligomer as a
coreactant. Those skilled in the art will recognize the benefits to
be gained through coreactive oligomer blends. The ethersulfone
toughens the relatively stiff and rigid heterocycle oligomers,
which is particularly important for the preparation of films.
To prepare ethers, the phenol or halide end cap is mixed with
suitable diols and dihalogens or with suitable dinitrohydrocarbons
and diols. To prepare esters, the phenol end cap or acid halide end
cap is mixed with suitable diols and diacids, both as will be
explained in greater detail later in this specification.
5. Etherimides
The polyetherimides and polysulfoneimides of the present invention
are analogous to the oligomers described in U.S. Pat. Nos.
4,851,495 and 4,981,922 and have the general formula: ##STR65##
wherein .rho.=--O-- or --S--;
.xi.=the residue of an end cap;
R.sub.11 =a trivalent C.sub.(6-13) aromatic organic radical;
R.sub.13 =a divalent C.sub.(6-30) aromatic organic radical; and
m=a small integer (the "polymerization factor") typically from
1-5.
We prepare the polyetherimide oligomers by several reaction
schemes. One method for synthesizing the polyetherimides involves
the simultaneous condensation of about 2m+2 moles of nitrophthalic
anhydride with about m+1 moles of diamine, about m moles of a diol,
and the extended amine end cap or the extended phenol end cap in a
suitable solvent under an inert atmosphere. The diol may actually
be in the form of a phenate.
In this reaction, the diamines (which preferably have aromatic
ethersulfone backbones) react with the anhydride of the
nitrophthalic anhydride to form dinitro intermediates and the diol
reacts with the nitro-functionality to form an ether linkage as
described in our U.S. Pat. Nos. 4,851,495 and 4,981,922. The end
caps quench the polymerization.
Another method comprises the simultaneous condensation of:
##STR66## in the ratio of XII:XIII:XIV;XV=1:1:m:m, wherein v=halo-
or nitro. The product has the general formula previously described.
The reaction conditions are generally comparable to those described
in U.S. Pat. Nos. 3,847,869 and 4,107,147.
Alternatively, we prepare the polyetherimides by reacting a
polyetherimide polymer made by the self-condensation of a
phthalimide salt of the formula: ##STR67## wherein M.sub.2 is an
alkali metal ion or ammonium salt or hydrogen with quenching
crosslinking end cap moieties of the formula: ##STR68## and a
halogeno cap of the formula: ##STR69## wherein Z is an end cap and
X is a halogen.
The self-condensation proceeds as described in U.S. Pat. No.
4,297,474 in a dipolar aprotic solvent. We introduce the end cap
moieties either during the self-condensation to quench the
polymerization or following completion of the polymerization and
recovery of the polyetherimide polymer from methanol (i.e.,
post-polymerization capping).
Another etherimide synthesis comprises the simultaneous
condensation of about 2m+2 moles of nitrophthalic anhydride with
about m+1 moles of diol, m moles of diamine, and 2 moles of the
extended amine end cap in a suitable solvent under an inert
atmosphere.
In any of the syntheses, we can replace the diol by a comparable
disulfhydryl. We can use mixtures of diols and disulfhydryls, of
course, but we prefer pure diols.
We can synthesize the oligomers in a homogeneous reaction scheme
wherein all the reactants are mixed at one time (and this scheme is
preferred), or in a stepwise reaction. We can mix the diamine and
diols, for example, followed by addition of the nitrophthalic
anhydride to initiate the polymerization and thereafter addition of
the end caps to quench it. Those skilled in the art will recognize
the different methods that might be used. To the extent possible,
we minimize undesirable competitive reactions by controlling the
reaction steps (i.e., addition of reactants) and the reaction
conditions.
Although we can use any diol (i.e., bisphenol) previously
described, for etherimides, we prefer a diol selected from the
those described in U.S. Pat. Nos. 4,584,364; 3,262,914; or
4,611,048 or a polyaryl diol selected from the group consisting
of:
HO--Ar--OH;
HO--Ar--.SIGMA.--Ar'--.SIGMA.--Ar--OH;
HO--Ar'--.SIGMA.--Ar--.SIGMA.--Ar'--OH;
wherein Y=--CH.sub.2 --, --(Me).sub.2 C--, --(CF.sub.3).sub.2 C--,
--O--, --S--, --SO.sub.2 -- or --CO--; ##STR70##
R.sub.1 =lower alkyl, lower alkoxy, aryl, aryloxy, substituted
alkyl, substituted aryl, halogen, or mixtures thereof;
g=0-4;
k=0-3; and
j=0,1,or2.
The preferred diols include hydroquinone; bisphenol-A;
p,p'-biphenol; 4,4'-dihydroxydiphenylsulfide;
4,4'-dihydroxydiphenylether; 4,4'-dihydroxy-diphenylisopropane; or
4,4'- dihydroxydiphenylhexafluoropropane. We prefer to use a single
diol rather than mixtures of diols. Actually, for the reactants in
any of our syntheses, we prefer to use a pure compound rather than
a mixture. We often seek the highest purity available for the
selected reactant because we seek to make the highest MWs we can
synthesize.
We prefer bisphenol-A as the diol because of cost and availability.
The other diols can be used, however, to add rigidity to the
oligomer and can increase the solvent resistance. Random or a block
copolymers are possible by using mixed diols as the reactant, but
we do not prefer them.
In the coreactive oligomer blends (Section 15), we can use these
diols as the Z*.sub.k --B--Z*.sub.k oligomers wherein k=1.
Suitable diamines include those diamines described with reference
to the imide synthesis or elsewhere in this specification.
In at least one synthesis of the etherimides, a compound of the
formula: ##STR71## is an intermediate or reactant (i.e., it is a
halogeno end cap). We form this intermediate by reacting the
corresponding extended amine end cap with halo- or nitrophthalic
anhydrides described in U.S. Pat. Nos. 4,297,474 and 3,847,869,
which also are incorporated by reference.
We synthesize multidimensional etherimides by reacting the
anhydride hub with compounds of formulae (XII) through (XV),
previously described. Those skilled in the art will recognize other
mechanisms to make multidimensional etherimide oligomers based on
the mechanisms we illustrated for the imides and amideimides.
Our etherimide oligomers can be four functional capped homologs of
the ULTEM or KAPTON etherimides that are commercially
available.
6. Polysulfoneimides
We can prepare polysulfoneimide oligomers corresponding to the
etherimides and analogous to those described and claimed in U.S.
patent application Ser. No. 07/241,997 by reacting about m+1 moles
of a dianhydride with about m moles of a diamine and about 2 moles
of an extended amine end cap. The resulting oligomer has the
general formula: ##STR72## wherein R and R' are divalent aromatic
organic radicals having from 2-20 carbon atoms. R and R' may
include halogenated aromatic C.sub.(6-20) hydrocarbon derivatives;
alkylene radicals and cycloalkylene radicals having from 2-20
carbon atoms; C.sub.(2-8) alkylene terminated
polydiorganosiloxanes; and radicals of the formula: ##STR73##
wherein p=--CO--, --SO.sub.2 --, --O--, --S--, or C.sub.(1-5)
alkane, and preferably, --CH.sub.2 -- so that the sulfoneimide
remains aromatic. Comparable polymers, usable in blends of the
sulfonamides, are described in U.S. Pat. No. 4,107,147, which we
incorporate by reference. U.S. Pat. No. 3,933,862 describes other
aromatic dithio dianhydrides.
7. Polyamides
We prepare linear or multidimensional polyamides (i.e., arylates or
nylons) by condensing dicarboxylic acid halides (i.e., a diacid or
a dibasic acid) with diamines in the presence of an acid halide end
cap or extended amine end cap. These polyamides are analogous to
the polyamide oligomers U.S. Pat. Nos. 4,876,326; 5,109,105;
4,847,333 describe.
We prepare multidimensional amides by condensing a nitro, amine, or
acid halide hub with suitable diamines, diacid halides, and the
extended amine end cap or the acid halide end cap to form oligomers
of the general formulae:
wherein P=a residue of a diamine, Q=a residue of a diacid halide,
and a, t and w were previously defined.
Examples of proposed amide syntheses follow.
EXAMPLE 36
Prepare a multidimensional amide oligomer by reacting: ##STR74##
under an inert atmosphere to yield: ##STR75##
EXAMPLE 37
Prepare another multidimensional amide oligomer by reacting:
##STR76## under an inert atmosphere to yield: ##STR77##
EXAMPLE 38
Prepare a multidimensional amide oligomer by reacting: ##STR78##
for simply the acid hub, a diamine, and an acid halide end cap
monomer) under an inert atmosphere to yield: ##STR79##
Competitive side reactions between the reactants in Example 38 will
likely hinder the yield of this product and will make isolation of
the product difficult. We enhance yield by adding the reactants
serially, which might impair the physical properties of the
resulting oligomers or composites made from the oligomers.
EXAMPLE 39
Use a etheramine hub to make a multidimensional amide oligomer by
reacting: ##STR80## under an inert atmosphere to yield:
##STR81##
EXAMPLE 40
Prepare a multidimensional amide using an extended anhydride end
cap by reacting: ##STR82## under an inert atmosphere to yield:
##STR83##
EXAMPLE 41
React melamine with an extended anhydride end cap to yield:
##STR84##
EXAMPLE 42
Prepare another multidimensional amide oligomer by reacting about 1
mole of cyuranic acid halide with about 3 moles of phenylenediamine
and about 3 moles of the extended anhydride end cap to yield:
##STR85##
We expect better yield of the fully substituted hub by reacting the
anhydride with aminobenzoic acid and converting the free carboxylic
acid functionality to an amine followed by condensation of the
resulting extended amine with the acid halide hub.
8. Polyesters
We prepare polyesters by condensing the previously described diacid
halides and diols. The linear oligomers are four functional analogs
of those compounds described in U.S. patent application Ser. No.
07/137,493. We make multidimensional polyesters using phenol or
acid hubs (particularly cyuranic acid) with suitable diols and
diacid halides. These multidimensional polyester oligomers are
analogs of those compounds described in U.S. patent application
Ser. Nos. 07/167,656 and 07/176,518 or in U.S. Pat. Nos. 5,175,233
and 5,210,213. We prefer to use a thallium catalyst when making
multidimensional polyesters to ensure complete addition on the
hub.
Commercial polyesters, when combined with well-known dilutents,
such as styrene, do not exhibit satisfactory thermal and oxidative
resistance to be useful for aircraft or aerospace applications.
Polyarylesters (i.e., arylates) are often unsatisfactory. These
resins often are semicrystalline, making them insoluble in
laminating solvents, intractable in fusion, and subject to
shrinking or warping during composite fabrication. Those
polyarylesters that are soluble in conventional laminating solvents
often remain soluble in these same solvents in composite form,
thereby limiting their usefulness in aerospace structural
composites. The high concentration of ester groups contributes to
resin strength and tenacity, but also makes the resin susceptible
to the damaging effects of water absorption. High moisture
absorption by commercial polyesters can lead to distortion of the
composite when it is loaded at elevated temperature.
We prepare high performance, aerospace, polyester advanced
composites, however, using crosslinkable, end capped polyester
imide ether sulfone oligomers that have an acceptable combination
of solvent resistance, toughness, impact resistance, strength,
processability, formability, and thermal resistance. By including
Schiff base (--CH.dbd.N--), imidazole, thiazole, or oxazole
linkages in the oligomer chain, the linear, advanced composites can
have semiconductive or conductive properties when appropriately
doped.
Preferred linear polyethers or polyesters have the general
formula:
wherein.xi.=a crosslinkable end cap to improve the solvent
resistance of the cured oligomer in the advanced composite; and
A and B=linear residues of respective diacid halides and diols;
.A-inverted.=ether or ester; and
t=0-27 (i.e., it is the "polymerization factor").
Generally, A and B are linear aromatic moieties having one or more
aromatic rings, such as phenylene, biphenylene, naphthylene, or
compounds of the general formula:
wherein .lambda. is any of --CO--; --.O slashed.--; --S--;
--SO.sub.2 --; --(CH.sub.3).sub.2 C--, --(CF.sub.3).sub.2 C--;
--CH.dbd.N--, oxazole, imidazole, or thiazole. For most
applications, the linking groups will be selected from --SO.sub.2
--, --S--, --O--, --CO--, --(CH.sub.3).sub.2 C--, and
--(CF.sub.3).sub.2 C--. The oligomer usually is a polyester imide
ether sulfone.
A or B preferably have the general formula:
wherein .OMEGA.=--O--, --SO.sub.2 --, or --S--, provided that
.OMEGA.=--SO.sub.2 -- only if .PSI.=--SO.sub.2 --;
.PSI.=--CO-- or --SO.sub.2 --, and
.O slashed.=phenylene.
We usually prepare these polyester oligomers by reacting:
2 moles of a crosslinkable end cap acid halide;
n moles of an aromatic diacid halide or of a difunctional chain
including a plurality of aryl rings linked with at least one
linkage selected from the group consisting of --SO.sub.2 --, --O--,
--S--, --CO--, --(CH.sub.3).sub.2 C--, --(CF.sub.3).sub.2 C--, or
mixtures thereof throughout the chain, the chain having an acid
halide functionality on each end; and
n+1 moles of an aromatic bisphenol (i.e., a diol having terminal
--OH functionalities
or by reacting:
2 moles of a crosslinkable phenol end cap;
n+1 moles of an aromatic diacid halide or of a difunctional chain
including a plurality of aryl rings linked with at least one
linkage selected from the group consisting of --SO.sub.2 --, --O--,
--S--, --CO--, --(CH.sub.3).sub.2 C--, --(CF.sub.3).sub.2 C--, or
mixtures thereof throughout the chain, the chain having an acid
halide functionality on each end; and
n moles of an aromatic bisphenol.
We have previously described the suitable diacid and diol
reactants.
Because the aromatic polyester resins synthesized in accordance
with this invention have appreciable molecular weight between the
reactive groups, even in thermoset formulations, the oligomers will
retain sufficient plasticity to be processable during fabrication
prior to crosslinking of the end caps to thermoset composites. If
possible, we synthesize thermoplastic formulations with even higher
molecular weights. The polyesters preferably have MWs between about
5000-40,000, and, more preferably, between about 15,000-25,000.
We make a particularly preferred polyester oligomer of the present
invention by condensing a diacid halide with an excess of a diol to
form an extended diol having intermediate ester linkages. This
extended diol is then reacted with excess
4,4'-dichlorodiphenylsulfone to yield a second intermediate
dihalogen. The dihalogen can be condensed with a phenol end cap or
the caps can be added in two steps by reacting the dihalogen with
(H.sub.2 N).sub.2 --.O slashed.--OH followed by reacting the
tetra-amine intermediate (i.e., bis(2,4-diaminophenyl)ether) with
an acid halide end cap from our U.S. Pat. No. 5,087,701. We prefer
nadic caps. This stepwise reaction is illustrated then, as follows:
##STR86## wherein E= ##STR87## and, particularly, ##STR88##
In this sequential or step-wise synthesis, the caps effectively
become: ##STR89## when the acid halide caps condense with the free
terminal amines on the extended ether/ester backbone (i.e., Cmpd.
3). Similar stepwise syntheses are available for reaction sequences
that can produce terminal acid halides (--COX), phenols (--OH), or
halides (--X), as will be understood from this single example.
Preferably, steps 2 and 3 are done simultaneously by combining the
diol of step 1 with the dihalogen and diaminophenol in a single
reaction flask.
Although illustrated in four steps, isolation and transfer between
steps is unnecessary until the product forms. An acid acceptor is
added incrementally at each step along with the sequential monomer
reactant. The product is isolated by precipitation in water with
water washing thereafter. The product is a phenoxy phenyl sulfone
alternating diester. Preferred diacid halides have D as ##STR90##
The preferred diols are those where A is ##STR91##
We can achieve glass transition temperatures of about 950.degree.
F. (510.degree. C.), although we can easily tailor the properties
of the resulting oligomers within broad ranges.
Preferred multidimensional ether or ester oligomers have a central,
aromatic hub and three, radiating, ether or ester chains, as shown
in the general formula: ##STR92## wherein .A-inverted.=ether or
ester;
w=3or4;
T=--O--, if .A-inverted.=--O--, ##STR93##
R=a linear hydrocarbon radical, generally including ether and
electronegative ("sulfone") linkages selected from the group
consisting of --SO.sub.2 --, --S--, --(CH.sub.3).sub.2 C--, --CO--,
and --(CF.sub.3).sub.2 C--, and generally being a radical selected
from the group consisting of: ##STR94##
n=an integer such that the average molecular weight of --R--T-- is
up to about 3000 (and preferably 0 or 1);
q=--CO--, --SO.sub.2 --, --(CF.sub.3).sub.2 C--, --(CH.sub.3).sub.2
C--, or --S--; and
.xi.=is a residue of multiple chemically functional acid halide end
cap or phenol end cap monomer;
We prepare multidimensional ether or ester oligomers of this type
by reacting substantially stoichiometric amounts of a
multi-substituted hub, such as trihydroxybenzene (i.e.,
phloroglucinol), with chain-extending monomers and crosslinking end
cap monomers. Suitable chain-extending monomers include
dicarboxylic acid halides, dinitro compounds, diols (i.e., dihydric
phenols, bisphenols, or dialcohols), or dihalogens, in the same
manner as making linear ethers or esters.
Multidimensional polyol hubs
The hub may be a polyol such as phloroglucinol or those
tris(hydroxyphenyl)alkanes described in U.S. Pat. No. 4,709,008 of
the general formula: ##STR95## wherein R.sub.15 is hydrogen or
methyl and can be the same or different. These polyols are made by
reacting, for example, 4-hydroxybenzaldehyde or
4-hydroxyacetophenone with an excess of phenol under acid
conditions (as disclosed in U.S. Pat. Nos. 4,709,008; 3,579,542;
and 4,394,469). We generally react the polyols with nitrophthalic
anhydride, nitroaniline, nitrobenzoic acid, or a diacid halide to
form the actual reactants (i.e., amines or acid halides) that are
suitable as heterocycle hubs, as will be understood by those of
ordinary skill.
We can use the extended acid hub: ##STR96## that we described
earlier. This hub is characterized by an intermediate ether and
imide linkage connecting aromatic groups. Thio-analogs are also
contemplated, in accordance with U.S. Pat. No. 3,933,862. Other
acid or polyol hubs are equally suitable.
Generally the ratio of reactants is about 1 mole of the hub to at
least 3 moles of end cap to at least 3 moles of polyaryl arms. The
arms usually include phenoxyphenyl sulfone, phenoxyphenyl ether, or
phenyl sulfone moieties to supply the desired impact resistance and
toughness to the resulting advanced composite (through "sulfone"
swivels) without loss of the desired thermal stability.
A second synthetic mechanism for making the multidimensional ether
oligomers involves the reaction of a halogenated or polynitro
aromatic hub with suitable amounts of diols and an extended acid
halide end cap monomer. Again, the reactants are mixed together and
are generally reacted at elevated temperatures under an inert
atmosphere. Generally for either mechanism, the reactants are
dissolved in a suitable solvent such as benzene, toluene, xylene,
DMAC, or mixtures and are refluxed to promote the reaction. We
sometimes add TEA to catalyze the reaction.
We also can make suitable oligomers by directly reacting polyol
hubs (such as phloroglucinol) or halogenated aromatic hubs directly
with end cap groups having the corresponding halide, acid halide,
or alcohol (phenol) reactive functionality.
Schiff base diols are prepared by the condensation of aldehydes and
amines under the general reaction schemes: ##STR97##
We prepare suitable dinitro compounds by reacting nitrophthalic
anhydride (as described in U.S. Pat. Nos. 4,297,474 and 3,847,869)
with a diamine. In this case, suitable diamines include those
described previously.
We prefer arms in the multidimensional oligomers that are short
chains having formula weights below about 1500 per arm, and,
preferably, about 500 per arm. Solubility of the oligomers becomes
an increasing problem as the length of the backbones (arms)
increases. Therefore, we prefer shorter backbones, so long as the
resulting oligomers remain processable. That is, the backbones
should be long enough to keep the oligomers soluble during the
reaction sequence.
We also can make noncrosslinking ether or ester linear or
multidimensional polymers for blends by the same synthetic methods
as the oligomers with the substitution of a quenching cap for the
crosslinking end cap. For example, phenol benzoic acid, or
nitrobenzene can be used to quench (and control MW).
The following are examples of proposed ester syntheses.
EXAMPLE 43
Prepare an ester star oligomer by dissolving phloroglucinol
dihydrate in a solution of H.sub.2 O and a solvent containing 27%
xylene and 73% DMAC. In a Barrett trap under a bubbling N.sub.2
atmosphere, reflux the mixture to strip off the H.sub.2 O and,
then, the xylene. After the stripping step, cool the resulting DMAC
solution slowly to about 0.degree. C. before adding triethylamine
(TEA) (30% excess) while stirring the solution. After 10 min. of
stirring, add an acid halide end cap monomer, and rinse the product
with DMAC. Continue stirring for 2 hours, before recovering a
product by adding a suitable amount of HCl.
EXAMPLE 44
Prepare another ester star oligomer by dissolving phloroglucinol
dihydrate in a xylene/DMAC mixture having about 740 g xylene and
2000 g DMAC. Reflux the mixture in a Barrett trap under a N.sub.2
atmosphere to strip H.sub.2 O, which the reaction generates. Upon
heating to about 160.degree. C., strip the xylene from the mixture.
Cool the DMAC solution to ambient, and add a phenol end cap monomer
and TEA. Stir the resulting mixture in an ice bath while adding the
acid chloride of bis-(4,4'-carboxyphenoxyphenylsulfone) is slowly.
After the addition, continue stirring for 2 hr. The product is
soluble in the reaction mixture, but coagulates in H.sub.2 O to a
powder. Wash the powder with deionized water to remove residual
chloride.
We have found that, when reacting, for example, phloroglucinol with
an acid chloride end cap in DMAC and TEA that the resulting product
is a mixture of di- and tri- substituted multidimensional ester
oligomers. The condensation is difficult to drive to completion
(i.e., replacement of all the --OH groups) to yield the desired
product. We improve the yield of fully reacted multidimensional
ester, however, by replacing the TEA with thallium ethoxide
(T1--OC.sub.2 H.sub.5). While thallium ethoxide is preferred, it is
possible that any lower alkoxy or aryloxy substituent on the metal
will be active as a catalyst. That is, methoxy, propoxy,
isopropoxy, n-butoxy, phenoxy, or the like may also display
catalytic activity.
Since the multidimensional polyester oligomers that we synthesize
are often used without isolation of products (so we have complex
mixtures in the prepreg), we believe that the new product made
using a thallium catalyst, richer in the truly multidimensional
ester product, will yield better composites than we achieved with
the mixture of fully and partially reacted hubs that results when
using TEA as a catalyst. In effect, the product is a blend of a
linear and a multidimensional oligomer when the reaction is
incomplete.
The method of using a thallium catalyst is equally applicable when
using an acid halide hub such as cyuranic acid chloride with an
extended phenol end cap monomer.
We believe that T1--OC.sub.2 H.sub.5 will produce a higher yield of
the tri-substituted hub. If the hub has more than three reactive
hydroxyl or acid halide functionalities, the thallium ethoxide
catalyst will promote more complete reaction (or substitution) than
TEA.
9. Polyethers
We prepare polyethers or ethersulfones by condensing dinitro
compounds or dihalogens and diols or by other conventional ether
syntheses using a phenol end cap monomer or a halogeno end cap
monomer.
We can use any previously described dihalogen.
We can prepare dinitro compounds by reacting nitrophthalic
anhydride with the diamines, as we previously described. Of course,
we can prepare dihalogens in the same way by replacing the
nitrophthalic anhydride with halophthalic anhydride. We can
condense nitroaniline, nitrobenzoic acid, or nitrophenol with
dianhydrides, diacid halides, diamines, diols, or dihalogens to
prepare other dinitro compounds that include amide, imide, ether,
or ester linkages between the terminal phenyl radicals and the
precursor backbones. The synthesis of the dinitro compounds or
dihalogens can occur prior to mixing the other reactants with these
compounds or the steps can be combined in suitable circumstances to
directly react all the precursors into the oligomers. For example,
we can prepare a polyarylether oligomer by simultaneously
condensing a mixture of the phenol end cap, nitrophthalic
anhydride, phenylene diamine, and HO--.O slashed.--O--.O
slashed.--O--.O slashed.--O--.O slashed.--OH.
We can prepare a multidimensional ether by the simultaneous
condensation of phloroglucinol with a dihalogen and a phenol end
cap monomer. Those of ordinary skill will recognize the range of
possible multidimensional polyether oligomers from this simple
example.
We can also synthesize multidimensional oligomers of the
formula:
and
with an Ullmann aromatic ether synthesis followed by a
Friedel-Crafts reaction, as will be further explained.
Here, R.sub.16 is ##STR98## q=--SO--, --CO--, --S--, or
--(CF.sub.3).sub.2 C--, and preferably --SO.sub.2 --, or
--CO--.
To form the oligomers for formula (XIX), preferably a
halosubstituted hub is reacted with phenol in DMAC with a base
(NaOH) over a Cu Ullmann catalyst to produce an ether "star" with
active hydrogens para- to the ether linkages. End caps terminated
with add halide functionalities can react with these active aryl
groups in a Friedel-Crafts reaction to yield the desired product.
For example, we react 1 mole of trichlorobenzene with about 3 moles
of phenol in the Ullmann ether reaction to yield an intermediate of
the general formula: .O slashed..brket open-st.O--.O
slashed.].sub.3 which we, then, react with about 3 moles of the
extended acid halide end cap to produce the final, crosslinkable,
ether/carbonyl oligomer.
Similarly, to form the oligomers of formula (XIX), the hub is
extended preferably by reacting a halo- substituted hub with phenol
in the Ullmann ether synthesis to yield the ether intermediate of
the .O slashed..brket open-st.O--.O slashed.].sub.3 compounds. This
intermediate is mixed with the appropriate stoichiometric amounts
of a diacid halide of the formula XOC--R.sub.16 --COX and an end
cap of the formula (Z).sub.2 --.O slashed.[formula (XX)] in the
Friedel-Crafts reaction to yield the desired, chain-extended
ether/carbonyl star and star-burst oligomers. We prepare end caps
of this type by reacting 2 moles of Z--COOH or its acid halide with
.O slashed..paren open-st.NH.sub.2).sub.2.
We can use coreactants with the ether or ethersulfone oligomers or
coreactive oligomer blends that include these oligomers, including
p-phenylene-diamine; 4,4'-methylenedianiline; benzidine; lower
alkyldiamines; or compounds of the general formula: ##STR99##
wherein R.sub.17 =hydrogen, lower alkyl, or aryl; and
R.sub.18 =lower alkyl (having about 2-6 carbon atoms) or aryl.
Coreactants of this same general type are also probably usable with
the amideimides or etherimides.
EXAMPLE 45
Prepare an ether star oligomer by charging DMAC, xylene, K.sub.2
CO.sub.3, and a multiple chemically functional phenol end cap to a
reaction flask fitted with a stirrer, condenser, thermometer, and
N.sub.2 purge. Add phloroglucinol dihydrate and reflux the mixture
until all H.sub.2 O in the flask is expelled and no additional
H.sub.2 O is generated. After cooling the resulting intermediate
mixture, add about 3.0 moles of 4,4'-dichlorodiphenylsulfone and
reheat the flask to about 150.degree. C. to strip the xylene from
the solution. Continue refluxing for 16 hours at about 150.degree.
C. Upon removal of all the xylene, heat the flask to about
160-164.degree. C. for 2 more hours. After cooling, recover the
product by adding H.sub.2 O to induce coagulation while mixing the
solution in a Waring blender. Wash the coagulate thoroughly with
deionized water until the residual chloride is removed.
10. Polyaryl sulfide oligomers (PPS)
We can also prepare multiple chemically functional oligomers of the
present invention for PPS backbones. These four functional
oligomers are analogs of the reactive PPS oligomers we described in
U.S. patent application Ser. No. 07/639,051.
A brief description of the state of the art for PPS resins is an
appropriate introduction.
Edmonds U.S. Pat. No. 3,354,129 describes the preparation of
poly(arylene sulfide) polymers by the reaction of an alkali metal
sulfide with a polyhalo-substituted aromatic (preferably
dihaloaromatic) compound wherein the halogen atoms are attached to
ring carbon atoms in a polar organic compound at elevated
temperature. A copper compound, such as cuprous and cupric
sulfides, or halides, may be present to aid in the formation of the
polymer. Molecular weight of the polymer is increased by heat
treatment, either in the absence of oxygen or with an oxidizing
agent. Molecular weight is increased due to crosslinking,
lengthening of the polymer chain, or both.
Campbell U.S. Pat. No. 3,919,177 discloses the preparation of
p-phenylene sulfide polymers by reacting p-dihalobenzene, a
suitable source of sulfur, an alkali metal carboxylate, and a
preferably liquid organic amide. Both of the alkali metal
carboxylate and the organic amide components serve as
polymerization aids. The alkali metal carboxylate may typically be
lithium acetate, lithium propionate, sodium acetate, potassium
acetate, or the like. The organic amide may typically be formamide,
acetamide, N-methylformamide, or N-methyl-2-pyrrolidone (NMP). A
variety of sulfur sources can be used, including alkali metal
sulfides, thiosulfates, thiourea, thioamides, elemental sulfur,
carbon disulfide, carbon oxysulfide, thiocarbonates,
thiocarbonates, mercaptans, mercaptides, organic sulfides, and
phosphorus pentasulfide.
Crouch et al. U.S. Pat. No. 4,038,261 describes a process for the
preparation of poly(arylene sulfide)s by contacting
p-dihalobenzene, a polyhalo aromatic compound having greater than
two halogen substituents, an alkali metal sulfide, lithium
carboxylate or LiCl, NMP, and an alkali metal hydroxide. The use of
a polyhalo compound results in the formation of a branched chain
polymer of reduced melt flow that can be spun into fibers. The
alkali metal sulfide can be charged to the reaction in hydrated
form or as an aqueous mixture with an alkali metal hydroxide.
Gaughan U.S. Pat. No. 4,716,212 describes the preparation of
poly(arylene sulfide ketones by reaction of a polyhalobenzophenone
such as 4,4'-dichlorobenzo-phenone and a mixture of sodium
hydrosulfide and sodium hydroxide.
Satake et al. U.S. Pat. Nos. 4,895,892 and 4,895,924 both disclose
melt stable poly(arylene thioether ketone)s. The '892 patent
describes blends of an arylene thioether ketone polymer with a
thermoplastic resin such as poly(arylene thioether)s, aromatic
polyether ketones, polyamides, polyamideimides, polyesters,
polyether sulfones, polyether imides, poly(phenelyene ether)s,
polycarbonates, polyacetals, fluoropolymers, polyolefins,
polystryrene, polymethyl methacrylate, ABS, and elastomers such as
fluororubbers, silicone rubbers, polyisobutylenes, hydrogenated
SBR, polyamide elastomers and polyester elastomers. U.S. Pat. No.
4,895,924 patent discloses the preparation of poly(arylene
thioetherketone) fibers by melt spinning of polymers and blends of
the type disclosed in U.S. Pat. No. 4,895,892.
Blackwell U.S. Pat. No. 4,703,081 describes a ternary polymer alloy
comprising a poly(arylene sulfide), a poly(amideimide) and a
poly(aryl sulfone). The poly(arylene sulfide) is prepared, for
example, by reaction of p-dichlorobenzene and sodium sulfide in
NMP. Various other di- and tri- halo aromatics are mentioned as
monomers for use in the preparation of the poly(arylene
sulfide)s.
Johnson et al. U.S. Pat. No. 4,690,972 describes the preparation of
poly(arylene sulfide) compositions by incorporating additives which
affect the crystalline morphology, followed by heating and cooling
steps. Among the preferred arylene sulfides are poly(phenylene
sulfide) and poly(phenylene sulfide ketone). The additive is
preferably a poly(arylene ether ketone) such as
1,4-oxyphenoxy-p,p'-benzophenone.
Leland et al. U.S. Pat. No. 4,680,326 describes poly(arylene
sulfide) compositions having a combination of good cracking
resistance and electrical insulation resistance. The compositions
include a reinforcing material, polyethylene, and an
organosilane.
Skinner U.S. Pat. No. 4,806,407 describes blends of p-phenylene
sulfide polymers and melt extrudable polymers such as
non-halogenated polymers and copolymers of olefins, halogenated
homopolymers (polyvinylidene fluoride, polyvinyl chloride,
polychlorotrifluoroethylene, and the like), ethylene/acrylic
copolymers (e.g., "Surlyn"), and both aromatic and aliphatic
polyamides.
We incorporate these PPS patents by reference.
The present invention provides oligomers useful in the preparation
of poly(arylene sulfide) [PPS] polymers having favorable
thermomechanical and thermooxidative properties, having other
advantageous performance properties, and having favorable
processing characteristics in the preparation of such composites.
The composites have high solvent resistance, moisture resistance,
toughness, and impact resistance.
We react (n) equivalents of a dihaloaromatic compound, (n+1)
equivalents of a sulfur compound that is reactive with the
dihaloaromatic compounds to form thioethers, and 2 equivalents of
the halogeno (i.e., halide) end cap monomer to obtain an oligomer
corresponding to the formula: ##STR100## where:
Ar and Ar.sub.1 are arylene;
.mu. is an integer such that the oligomer has about molecular
weight of between about 500 and about 40,000;
.xi. is a residue of a halogeno end cap monomer, and the other
variables are as previously defined.
We prepare composites from the oligomers in the form of films,
coatings, moldings, fibers, and other structures useful in
engineering applications. We expect that PPS composites produced
from these oligomers will exhibit exceptional toughness and impact
resistance for PPS.
When used for preparation of various forms of polymer products, the
oligomers of the invention exhibit especially favorable processing
characteristics. Their melt and plastic flow properties are
especially advantageous for the preparation of moldings and
composites without the necessity of solvents. Because the oligomers
crosslink by an addition of "step growth" mechanism, curing of
moldings or composites can be conducted without significant
outgassing of solvents or condensation products, thereby yielding
polymer products of exceptional structural and dimensional
integrity. Adhesives comprising the oligomers of the invention, and
the polymeric products obtained by curing thereof, we can prepare
without outgassing of either reaction products or solvents.
The oligomers are crosslinkable by addition or step growth reaction
of the unsaturated moieties of the end caps analogous to the PPS
oligomers of Ser. No. 07/639,051. In this respect they differ from
the polymers of U.S. Pat. No. 3,354,129, which are crosslinked
through functional groups provided in the linear backbone, and from
the polymers of U.S. Pat. No. 4,038,261, in which linear chains are
branched and crosslinked by incorporation of a minor proportion of
trihaloaromatic compound in a polymerization mixture comprising
p-dihalobenzene and sulfur compound.
We can prepare oligomers of the present invention in both linear
and multidimensional form. We prepare the linear oligomers by
reacting n equivalents of a dihaloaromatic compound (i.e., a
dihalogen), n+1 equivalents of a sulfur compound that is reactive
with the dihalo-aromatic compounds to form thioethers, and 2
equivalents of halogeno end cap monomer. Crosslinking of the
oligomer may subsequently take place under curing conditions. The
multidimensional oligomers, of course, use an appropriate hub.
Generally, the sulfur compound used in the preparation of the
oligomer is characterized by its reactivity with halo organic
compounds to produce thioethers. Preferably, the sulfur compound
comprises an alkali metal sulfide, an alkali metal sulfohydride, or
an alkali metal bisulfide. Among the various other sulfur compounds
which may optionally be used in the reaction are alkali metal
thiosulfates, thioamides, elemental sulfur, carbon disulfide,
carbon oxysulfide, thiocarbonates, thiocarbonates, mercaptans,
mercaptides, organic sulfides and phosphorus pentasulfide. If the
sulfur compound used is other than an alkali metal sulfide or
bisulfide, we include a base in the reaction charge. If the sulfur
compound is an alkali metal bisulfide, the use of a base is not
strictly necessary, but we prefer to include it. If the sulfur
compound is an alkali metal sulfide, a base is unnecessary.
For the PPS synthesis, preferred dihalogens include:
1,2-dichlorobenzene
1,3-dichlorobenzene
1,4-dichlorobenzene
2,5-dichlorotoluene
1,4-dibromobenzene
1,4-diodobenzene
1,4-difluorobenzene
2,5-dibromoaniline
1,4-di-n-butyl-2,5-dichlorobenzene
1,4-di-n-nonyl-2,6-dibromobenzene
2,5-dichlorobenzamide
1-acetamido-2,4-dibromoanphthalene
4,4'-dichlorodiphenyl
p-chlorobromobenzene
p,p'-dichlorodiphenylether
o,p'-dibromodiphenyl amine
4,4'-dichlorobenzophenone and
4,4'-dichlorodiphenylsulfone.
We could use any dihalogen we described earlier.
Preparation of the oligomer is preferably carried out in the
presence of a polymerization aid such as a liquid organic amide, a
carboxylic acid salt, or both. In the preparation of conventional
poly(arylene sulfide) polymers, such aids are effective in
increasing the average MW of the polymerization product. In the
process of the invention, such polymerization aids are effective in
controlling and limiting the molecular weight distribution within a
narrow range of variability.
Conditions for carrying out the reaction to form the oligomer are
essentially the same as those described in U.S. Pat. Nos. 3,354,129
and 3,919,177. The reaction may be carried out, for example, by
contacting the dihalogen, the sulfur compound, and the end cap
monomer in a polar solvent at a temperature of from about
125.degree. to about 450.degree. C., preferably from about
175.degree. to about 350.degree. C. The amount of polar solvent may
vary over a wide range, typically from about 100 to about 2500 ml
per mole of the sulfur compound.
Alkali metal carboxylates that may be employed in the reaction
generally correspond to the formula:
where R.sub.20 is a hydrocarbyl radical selected from alkyl,
cycloalkyl, and aryl and combinations thereof such as alkylaryl,
alkylcycloalkyl, cycloalkylalkyl, arylalkyl, arylcycloalkyl,
alkylarylakyl and alkylcycloalkylalkyl, the hydrocarbyl radical
having 1 to about 20 carbon atoms, and M.sub.3 is an alkali metal
selected from the group consisting of lithium, sodium, potassium,
rubidium and cesium. Preferably, R.sub.20 is an alkyl radical
having 1 to about 6 carbon atoms or a phenylene radical. Most
preferably, it is phenylene. M.sub.3 is lithium or sodium, most
preferably lithium. If desired, employ the alkali metal carboxylate
as a hydrate or as a solution or dispersion in water.
Examples of some alkali metal carboxylates that we might use in the
process include lithium acetate, sodium acetate, potassium acetate,
lithium propionate, sodium propionate, lithium 2-methylpropionate,
rubidium butyrate, lithium valerate, sodium valerate, cesium
hexanoate, lithium heptanoate, lithium 2-methyloctanoate, potassium
dodecanoate, rubidium 4-ethyltetradecanoate, sodium octadecanoate,
lithium cyclohexanecarboxylate, cesium cyclododecanecarboxylate,
sodium 3-methlcyclopentanecarboxylate, potassium cydohexylacetate,
potassium benzoate, lithium benzoate, sodium benzoate, potassium
m-toluate, lithium phenylacetate, sodium
4-phenylcyclohexanecarboxylate, potassium p-tolylacetate, lithium
4-ethylcyclohexylacetate, and the like, or mixtures thereof.
The organic amides used in the method of this invention should be
substantially liquid at the reaction temperatures and pressures.
Examples of some suitable amides are N,N-dimethylformamide,
N,N-dipropylbutyramide, N-methyl-.xi.-caprolactam,
hexamethyl-phosphoramide, tetramethylurea, and the like, or
mixtures thereof.
When we use alkali metal carboxylates and organic amides for
control of the oligomer formation reaction, we carry out the
reaction at about 235.degree. C. and about 450.degree. C.,
preferably about 240.degree. C. to about 350.degree. C. When the
alkali metal carboxylate is a sodium, potassium, rubidium, or
cesium salt of an aromatic carboxylic acid, i.e., an acid in which
the carboxyl group is attached directly to an aromatic nucleus, the
temperature should be within the range of from about 255.degree. C.
to about 450.degree. C., preferably from about 260.degree. C. to
about 350.degree. C. The reaction time is within the range of from
about 10 minutes to about 3 days and preferably about 1 hour to
about 8 hours. Preferably, we use about 0.5 to about 2 moles metal
carboxylate compound per mole of the dihaloaromatic compound. When
we use NMP as the organic amide component of the reactor charge, we
use it in substantially equal molar proportion with the dihalogen
compound.
We use the PPS oligomers in melt or solution form for the
preparation of films, moldings, and composites. Curing at a
temperature in the range of between about 480.degree. and about
640.degree. F. (250 to 340.degree. C.) causes step growth reaction
between the unsaturated moieties of the end groups, resulting in
the formation of high molecular weigh polymers having superior
thermal and mechanical properties and solvent resistance. We
initiate the curing reaction either thermally or chemically. Where
the oligomer has a relatively high molecular weight, for example,
greater than 10,000, preferably about 15,000 to 25,000, the polymer
produced on curing is thermoformable. Where the molecular weight is
below 10,000, especially in the range of between about 1000 and
about 6000, the cured resin is likely a thermoset material, which
we seek to avoid.
We prepare multidimensional PPS oligomers by reacting w(n)
equivalents of a dihalogen, w(n+1) equivalents of a sulfur compound
that is reactive with dihalogen to form thioethers, one equivalent
of a polyhalo hub having w halogen substituents, and w equivalents
of a halogeno end cap monomer.
In the preparation of either linear or multidimensional PPS
oligomers, it is generally preferred that the dihalogen comprises a
dihalobenzene such as, for example, p-dichlorobenzene or
m-dichlorobenzene, and the sulfur compound be an alkali metal
sulfide such as sodium sulfide, which can be prepared in situ by
reaction of an alkali metal hydrosulfide and a base. An
advantageous method for the preparation of arylene sulfide
oligomers from an alkali metal hydrosulfide is described in U.S.
Pat. No. 4,716,212.
We can make blends suitable for composites, for example, by mixing
a PPS oligomer of the invention with a macromolecular or oligomeric
polymer that is essentially incapable of crosslinking with the
crosslinkable oligomer. Such blends merge the desired properties of
crosslinking oligomers and non-crosslinking polymers to provide
tough, yet processable, resin blends. We can use a variety of
macromolecular or oligomeric polymers, most typically a
poly(arylene sulfide) prepared by reaction of a dihalogen with a
sulfur compound of the type used in the preparation of the
oligomer, the reaction being quenched with a suitable
non-crosslinking terminal group. Generally, we would prepare such
poly(arylene sulfide)s by the methods described in U.S. Pat. Nos.
3,354,129, 3919,177, and 4,038,261. Most preferably, we would
prepare the non-crosslinking polymer and crosslinkable oligomer
from the same dihaloaromatic and sulfone compound, thus enhancing
compatibility between oligomer and polymer. The quenching agent is
typically a monohaloaromatic compound such as chlorobenzene.
The blends also encompass the advanced composites blends of
poly(arylene sulfide) oligomers blended with poly(amide imide)s and
poly(aryl sulfone)s analogous to the blends described in U.S. Pat.
No. 4,703,081. Blends may also comprise the various polymers used
in the blends described in U.S. Pat. No. 4,595,892.
The melt flow characteristics of PPS oligomers are such that PPS
may be used in melt rather than solution form in various
applications, including the preparation of composites. In this
regard, PPS is similar to the heterocycle liquid crystals.
For maximum mechanical properties of coatings or composites
prepared from PPS oligomers or blends, we prefer that the halogeno
substituents of the dihalogen have a predominantly p-orientation.
For processability, however, the most favorable results are
generally provided by use of the m-isomer, so processing and final
properties compete, forcing a trade when designing the formulation.
The m-isomer may also be preferable for adhesives. In certain
instances, it may be advantageous to provide a blend of m- and
p-isomers having a mix of properties tailored to the particular
application of the cured oligomer.
The end cap monomer can be ##STR101## (i.e., a pyrimidine cap) when
making these PPS oligomers or their related polyethers.
The following examples illustrate the invention with respect to PPS
oligomers.
EXAMPLE 46
Place hydrated Na.sub.2 S in N-methylpyrrolidone (NMP) in a glass
reaction flask and heat to 160.degree. C. while the flask is
flushed with nitrogen for a time sufficient to dehydrate the
Na.sub.2 S. Add p-dichlorobenzene (88.2 g) and a halogeno end cap
monomer to the dehydrated solution, and the resulting mixture is
sealed in a glass tube. The mixture contained in the tube is heated
at 230.degree. C. for 45 hours, then at 225.degree. C. for 20
hours, and then at 260.degree. C. for 24 hours. A product
precipitating from the reaction mixture comprises a four functional
PPS oligomer.
EXAMPLE 47
Prepare a multidimensional PPS oligomer by reaction of Na.sub.2 S,
p-dichlorobenzene, 1,3,5-trichlorobenzene, and a halogeno end cap
monomer. The preparation procedure is substantially as described in
Example 51, except that the trichlorobenzene is added together with
the p-dichlorobenzene and the end cap.
11. Carbonates
We prepare multiple chemically functional carbonate oligomers by
reacting a diol (sometimes also referred to as a dihydric phenol),
a carbonyl halide, and a phenol end cap in a manner similar to the
reaction described in U.S. Pat. No. 4,814,421, which is
incorporated by reference. While we can use any diol, we prefer
diols having the formula:
wherein A is (i) a divalent hydrocarbon radical containing 1-15
carbons,
(ii) a halogen substituted divalent hydrocarbon radical containing
1-15 carbons, or
(iii) divalent groups such as --S--, --SS--, --SO.sub.2 --, --SO--,
--O--, or --CO--.
We prefer the aromatic diols, especially the diol: HO--.O
slashed.--SO.sub.2 --.O slashed.--OH.
The carbonyl halide is a carbonate precursor and commonly is
phosgene, but the reaction can also use a diarylcarbonate or a
bishaloformate of a dihydric phenol or of a glycol.
The reaction proceeds by interfacial polymerization as described in
U.S. Pat. Nos. 3,028,365; 3,334,154; 3,275,601; 3,915,926;
3,030,331; 3,169,121; 3,027,814; and 4,188,314, which are
incorporated by reference. Generally the phenol reactants are
dissolved or dispersed in aqueous caustic, adding the mixture to a
water immiscible solvent, and contacting the reactants thereafter
with the carbonate precursor in the presence of a catalyst and
under controlled pH conditions.
The catalyst is usually a tertiary amine (like TEA), quaternary
phosphonium compounds, or quarternary ammonium compounds.
The water immiscible solvents include methylene chloride,
1,1-dichloroethane, chlorobenzene, toluene, or the like.
The reaction can also be used to make mono- and difunctional
polycarbonate oligomers by substituting an imidophenol end cap
monomer from our U.S. Pat. Nos. 4,980,481; 4,661,604; 4,739,030;
and 5,227,461 for the four functional phenol end cap monomer. The
difunctional imidophenol end cap monomers have the general formula:
##STR102## where E is an unsaturated hydrocarbon as previously
defined.
We can prepare arylate/carbonate copolymers by the reaction of
phosgene with diacid halides in the solvent phase with a diol like
bisphenol-A in the solute phase using 3,5-di(nadicylimino)benzoyl
chloride or the extended add halide end cap monomer, and can
prepare multidimensional carbonates using a suitable polyhydric hub
like phloroglucinol. Multidimensional arylate/carbonates, of
course, can use an acid or acid halide hub, like cyuranic acid.
Those skilled in the art will recognize the mechanisms which are
analogous to those for our other linear and multidimensional
oligomers.
Step wise condensation similar to the four-step process described
for the esters will also lead to carbonates. Here, a long-chain
four functional amine having intermediate, characteristic carbonate
linkages is formed by condensing the diol with a carbonyl halide
and ##STR103## followed by reaction of the four terminal amines
(i.e., two at each end of the chain in the carbonate compound):
##STR104## With an acid halide end cap monomer (see, e.g., U.S.
Pat. No. 5,087,701) to yield the Z links of the characteristic four
functional end caps.
12. Polyesteramides
The linear oligomers are characterized by having a pair of
alternating ester linkages ##STR105## followed by a pair of
alternating amide linkages ##STR106## as generally illustrated for
polymeric homologs in U.S. Pat. No. 4,709,004 or by having
sequential amide/ester linkages. The preferred esteramides are
prepared by condensing an amino/phenol compound (like aminophenol;
preferably, 4-[2-p-hydroxyphenyl)isopropyl]-4'-amino diphenyl
ether) or other amino/phenols described in U.S. Pat. No. 4,709,004
with a diacid halide, especially terephthaloyl chloride, and four
functional acid halide end cap monomer following generally the
process of Imai et al. in J. Polymer Sci., 1981, 19, pp. 3285-91
which is discussed in U.S. Pat. No. 4,709,004 (both of which are
incorporated by reference). We alter the Imai process by using the
end cap monomer to quench the reaction and to provide an oligomeric
product. In the preferred synthesis, the oligomer is likely to
include a mixture of the following recurring units: ##STR107## as
the diacid halide reacts in a head-to-tail sequence or
head/head-tail/tail sequence.
Multidimensional esteramides condense a polybasic acid, polyol, or
polyamine hub with a suitable end cap monomer or with arm
extenders, like the amino/phenol compounds, amino/acid compounds,
diacid halides, and diamines, as appropriate and as previously
described for the other resin systems.
13. Cyanates and Cyanate Esters
We can also apply the technique of multiple chemically functional
oligomer to the cyanate resin system. Typical resins in the cyanate
family are described in U.S. Pat. No. 5,134,421, which we
incorporate by reference. Cyanate resins are characterized by the
reactive functionality --OCN, but we use the term to include the
thio cyanate cousins --SCN as well. Cyanate resins are prepared by
reacting diols or polyols (in the case of multidimensional
morphology) with a cyanogen halide, especially cyanogen chloride or
bromide. The synthesis is well known and is described in U.S. Pat.
Nos. 3,448,079; 3,553,244; and 3,740,348, for example; each of
which is also incorporated by reference. The cyanate functionality
self-polymerizes to form cyanate esters either with or without a
suitable catalyst (such as tin octoate).
Therefore, to prepare linear cyanate oligomers of the present
invention, diols are converted to dycanate (i.e.,
N.tbd.C--O--R.sub.4 --O--C.tbd.N where R.sub.4 is the residue of an
organic diol) in the presence of cyanogen halide and the phenol end
cap monomers of formula (II) are also connected to the
corresponding cyanate using the same reaction. Then, the chain
terminating cyanate end cap is mixed with the cyanate to control
the self-polymerization which yields a cyanate ester having four
crosslinking sites at each end. The multidimensional synthesis is
analogous but involves a polyol hub converted to the cyanate, mixed
with the dicyanate and cyanate end cap monomer, and
polymerized.
Suitable catalysts for the cyanate resin systems of the subject
invention are well known to those skilled in the art, and include
the various transition metal carboxylates and naphthenates, for
example zinc octoate, tin octoate, dibutyltindilaurate, cobalt
naphthenate, and the like; tertiary amines such as
benzyldimethylamine and N-methylmorpholine; imidazoles such as
2-methylimidazole; acetylacetonates such as iron (III)
acetylacetonate; organic peroxides such as dicumylperoxide and
benzoylperoxide; free radical generators such as
azobisisobutyronitrile; organophoshines and organophosphonium salts
such as hexyldiphenylphosphine, triphenylphosphine,
trioctylphosphine, ethyltriphenylphosphonium iodide and
ethyltriphenylphosphonium bromide; and metal complexes such as
copper bis[8-hydroxyquinolate]. Combinations of these and other
catalysts may also be used.
Any diol we previously described can be converted to the cyanate
analog and used in this synthesis. For high MWs, however, we prefer
to use a soluble dicyanate, especially:
Similarly, any polyol hub we previously described can be converted
to the corresponding polycyanate analog to serve as the hub (a) in
the synthesis of multidimensional cyanate ester oligomers.
The thiocyanates exhibit essentially the same chemistry.
14. Advanced Composite Blends
Advanced composite blends comprise at least one crosslinking
oligomer and at least one polymer wherein the backbones of the
oligomer(s) and polymer(s) are from different chemical families.
Such blends present promise for tailoring the mechanical properties
of composites while retaining ease of processing. At their
simplest, the composites are mixed chemical blends of a linear or
multidimensional crosslinking oligomer of one chemical family, such
as a imide, and a linear or multidimensional polymer, unable to
crosslink, from a different chemical family, such as ethersulfone.
Generally the polymer has a MW that is initially higher than that
of the oligomer, but the formula weight of the oligomeric portion
of the blend will increase appreciably during curing through
addition (i.e. homo-) polymerization between the crosslinking
functionalities. The ratio of oligomer(s) to polymer(s) can be
varied to achieve the desired combination of physical properties.
Usually the ratio is such that the addition polymer (i.e.,
composite) formed during curing of the oligomer constitutes no more
than about 50 mol % of the total.
While two component blends are preferred, the blends can be more
complex mixtures of oligomers or polymers with or without
coreactants. The blends may even include coreactive oligomers as
will be explained (i.e., diamines, diols, or ##STR108## resins). We
can also form blends of these multiple chemically functional
oligomers with corresponding monofunctional or difunctional
oligomers from our earlier patents and patent applications.
The oligomer is preferably selected from imidesulfone;
ethersulfone; cyanate ester; carbonate; amide; esteramide; imide;
ether; ester; estersulfone; etherimide; or amideimide. That is, any
of the oligomers we have described.
In advanced composite blends oligomers or coreactive oligomer
blends are further blended with a noncrosslinking polymer having a
backbone from a different chemical family. The polymer can be from
any one of the families described for the oligomers, but the
oligomeric and polymeric backbones must be different to form what
we elect to call an advanced composite (i.e. mixed chemical) blend.
The resulting blend may yield IPN or semi-IPN morphology in the
consolidated resin (composite) state.
Preferably the polymer's MW initially is greater than that of the
oligomer, because the MW of the oligomer in the cured composite
will increase through addition polymerization. The cured composite
from an advanced composite blend will have a blend of two, "long"
molecules, and will not suffer from a broad distribution of MWs or
a mismatch of MW that reduces the physical properties obtainable in
some prior art blends, such as those Kwiatkowski suggested in U.S.
Pat. No. 3,658,939.
Preferred oligomer/polymer combinations in the advanced composite
blends of this invention include: amideimide/imide; imide/amide;
ester/amide; ester/imide; and ester/esteramide.
Advanced composite blends allow tailoring of the properties of high
performance composites. They allow averaging of the properties of
resins from different families to provide composites that do not
have as severe shortcomings as the pure compounds. The resulting
composites have a blending or averaging of physical properties,
which makes them candidates for particularly harsh conditions.
Although the concept of advanced composite blends is probably best
suited to linear morphology, the advanced composite blends of the
present invention also include multidimensional oligomers and
polymers. We prefer linear morphology because the resulting
composites have mixtures of polymers of relatively large and
roughly equivalent MW. The individual polymers are similar in
structure. We have found it difficult in many circumstances to
process multidimensional oligomers that have appreciable MW, so the
properties of composites made from multidimensional advanced
composite blends might suffer because of diversity of MW.
Furthermore, the addition polymerization reaction for
multidimensional oligomers results in formation of a complex,
3-dimensional network of crosslinked oligomers that is difficult or
impossible to match with the multidimensional polymers, because
these polymers simply have extended chains or short chains. That
is, upon curing, the multidimensional oligomers crosslink to
chemically interconnect the arms or chains through the end caps,
thereby forming a network of interconnected hubs with intermediate
connecting chains. The connecting chains have moderate MW, although
the oligomer can add appreciable MW upon curing. In contrast, the
polymer (which does not crosslink) simply has a hub with arms of
moderate MW. While, for linear morphology, the disadvantages of
blended composites that have a wide diversity of average MW
polymers as constituents can be overcome by curing relatively low
MW oligomers into relatively high MW cured polymers that are
roughly equivalent to the polymer constituents, the polymers in the
multidimensional morphology are likely to have average MW lower
than the oligomeric component. Therefore, we believe we can achieve
the best results for the present invention with systems having
linear morphology where it is easier to achieve MW harmony in the
composite.
Although we have yet to verify our theory experimentally, it may be
possible and desirable to synthesize the polymeric component of the
multidimensional advanced composite blend when curing the oligomer,
and, in that way, forming relatively comparable oligomeric and
polymeric networks. To achieve this effect, we would mix, for
example, a multidimensional oligomer with comparable polymeric
precursors, such as triamines and tricarboxylic acid halides. Upon
curing, the precursors would condense to form amide linkages to
form bridges between hubs in a manner comparable to the oligomeric
connecting chains.
The potential problem of structural mismatch and the proposed
solution for achieving comparable MW in multidimensional advanced
composite blends likely also applies to coreactive oligomer blends
to some degree so that homopolymerization and addition
polymerization compounds remain comparable.
To overcome the problem of different MW between the oligomer and
polymer in the composite, we theorize that it may be possible to
prepare a blend that includes the oligomer and polymeric
precursors. For example, we can mix a polyether oligomer of the
general formula: ##STR109## wherein .xi. is the residue of a four
functional end cap monomer with polyamide polymeric precursors of
the general formula: ##STR110## so that, upon curing, the oligomer
crosslinks and the polymeric precursors condense through the amine
and acid to form a polyamide polymer. This approach may be best
suited for the lower curing oligomers. The product may include
addition polymers and block copolymers of the oligomer and one or
both of the polymeric precursors. A Michaels addition might occur
between the oligomer and amine multidimensional polymer, which
would be undesirable.
The oligomers may be formed by the attachment of arms to the hub
followed by chain extension and chain termination. For example,
phloroglucinol may be mixed with p-aminophenol and
4,4'-dibromodiphenylsulfone and reacted under an inert atmosphere
at an elevated temperature to achieve an amino-terminated "star" of
the general formula: ##STR111## that can be reacted with suitable
diacid halides, dianhydrides, and end caps to yield an amide,
amideimide, imide, or other oligomer. By substituting
2,4-diaminophenol for aminophenol, an ethersulfone compound of the
formula: ##STR112## can be prepared. When reacted with an acid
halide end cap monomer to produce Z end groups the product is a
multiple chemically functional ether sulfone multidimensional
oligomer. Extended amides, imides, etc. could also be prepared
resulting in multidimensional oligomers with a high density of
crosslinking functionalities.
As we have discussed, the oligomers can be synthesized in a
homogeneous reaction scheme wherein all the reactants are mixed at
one time, or in a stepwise reaction scheme wherein (1) the
radiating chains are affixed to the hub and the product of the
first reaction is subsequently reacted with the end cap groups or
(2) extended end cap compounds are formed and condensed with the
hub. Homogeneous reaction is preferred, resulting undoubtedly in a
mixture of oligomers because of the complexity of the reactions.
The products of the processes (even without distillation or
isolation of individual species) are preferred oligomer mixtures
which can be used without further separation to form the desired
advanced composites.
We can synthesize linear or multidimensional oligomers from a
mixture of four or more reactants thereby forming extended chains.
Adding components to the reaction liquor, however, adds complexity
to the reaction and to its control. Undesirable competitive
reactions may result or complex mixtures of macromolecules having
widely different properties may form, because the mixed chain
extenders and chain terminators compete with one another.
The hub may also be a polyol such as those described in U.S. Pat.
No. 4,709,008. These polyols are made by reacting, for example,
4-hydroxybenzaldehyde or 4-hydroxyacetophenone with an excess of
phenol under acid conditions (as disclosed in U.S. Pat. Nos.
4,709,008; 3,579,542; and 4,394,469). The polyols may also be
reacted with nitrophthalic anhydride, nitroaniline, nitrophenol, or
nitrobenzoic acid to form other compounds suitable as hubs as will
be understood by those of ordinary skill.
In synthesizing the polymers, we use quenching compounds to
regulate the polymerization (i.e., MW) of the comparable polymer,
so that, especially for linear systems, the polymer has a MW
initially substantially greater than the crosslinkable oligomer.
For thermal stability, we prefer an aromatic quenching compound,
such as aniline, phenol, or benzoic acid chloride. We generally
make the noncrosslinking polymer by the same synthetic method as
the oligomer with the substitution of a quenching cap for the
crosslinking end cap. Of course, we may adjust the relative
proportion of the reactants to maximize the MW.
While the best advanced composite blends are probably those where
the individual oligomers and polymers in the blend are of modest MW
and those in which the oligomer and polymer are initially in
equimolar proportions, we can prepare other compositions, as will
be recognized by those of ordinary skill in the art. Solvent
resistance of the cured composite may decrease markedly if the
polymer is provided in large excess to the oligomer in the
blend.
The advanced composite blends may include multiple oligomers or
multiple polymers, such as a mixture of an amideimide oligomer, an
amide oligomer, and an imide polymer or a mixture of an amideimide
oligomer, an amideimide polymer, and an imide polymer (i.e. blended
amideimide further blended with imide). When we use polyimide
oligomers, the advanced composite blend can include a coreactant,
such as p-phenylenediamine, benzidine, or 4,4'-methylenedianiline.
Ethersulfone oligomers can include these imide coreactants or
anhydride or anhydride-derivative coreactants, as described in U.S.
Pat. No. 4,414,269. We can use other combinations of oligomers,
polymers, and coreactants, as will be recognized by those of
ordinary skill in the art.
As discussed above, the oligomeric component of the advanced
composite blend may itself be a blend of the oligomer and a
compatible polymer from the same chemical family, further blended
with the compatible polymer from the different family. The advanced
composite blends generally include only one oligomeric component
unless coreactive oligomers are used.
Advanced composite blends are illustrated as follows.
EXAMPLE 48
Proposed linear amideimide/ether advanced composite blend.
The polyamideimide oligomer of Example 10 is dissolved in a
suitable solvent. Make a relative high average formula weight
polyether polymer condensing the diol:
with Cl--.O slashed.--Cl and phenol (to quench the polymerization)
under an inert atmosphere in the same solvent as used with the
polyamideimide oligomer or another miscible solvent.
Mix the two solutions to form a lacquer of the advanced composite
blend. Prepreg or dry the lacquer prior to curing to an advanced
amideimide/ether composite.
EXAMPLE 49
Proposed multidimensional ether sulfone/ester advanced composite
blend.
Prepare a multidimensional, polyether sulfone polymer by reacting
phloroglucinol with Cl--.O slashed.--Cl and HO--.O slashed.--O--.O
slashed.--SO.sub.2 --.O slashed.--O--.O slashed.--OH, quenching the
polymerization with either .O slashed.--Cl or phenol to yield a
polymeric product. The condensation occurs in a suitable solvent
under an inert atmosphere. Do not recover the product from the
solvent.
Prepare a multidimensional, polyester oligomer in the same solvent
as used for the polymer or in another miscible solvent by
condensing cyuranic acid chloride with a phenol end cap. Do not
recover the product, but mix the oligomeric reaction mixture with
the polymer product to form a varnish of a multidimensional
advanced composite blend. Prepregg or dry the varnish prior to
curing to form a multidimensional, polyester/polyethersulfone,
advanced composite.
15. Coreactive oligomer blends
Block copolymers are promising for tailoring the mechanical
properties of composites while retaining ease of processing. The
present invention also comprises blends of two or more coreactive
oligomers analogous to those blends described in U.S. Pat. No.
5,159,055. The oligomers are terminated with mutually interreacting
caps that allow formation of the block copolymer(s) upon curing. We
can increase stiffness in this way in an otherwise flexible
oligomer, although the four crosslinks themselves increase
stiffness. For example, we can achieve stiffening for a composite
made from an ethersulfone oligomer by adding an imide oligomer as a
coreactant. Those skilled in the art will recognize the benefits to
be gained through coreactive oligomer blends. Generally, at least
one of the oligomers in the coreactive oligomer blend will include
four crosslinking functionalities at each end of the backbone.
We generally prepare block copolymers formed from the coreactive
oligomer blends by blending an oligomer of the general formula:
wherein R.sub.4 =a divalent hydrocarbon radical, as we have
described; and
.xi.=a four functional hydrocarbon residue of an end cap monomer
used to form the oligomer
with a coreactive oligomer of the general formula:
wherein k=1, 2, or 4;
B=a hydrocarbon backbone that is from the same or a different
chemical family as R.sub.4 ;
Z*=a hydrocarbon residue including a segment selected from the
group consisting of: ##STR113##
.rho.=--O-- or --S--;and
--.O slashed.--=is phenylene.
Preferably we select the oligomeric backbones from the group
consisting of imidesulfones, ethersulfones, carbonates,
esteramides, amides, ethers, esters, estersulfones, imides,
etherimides, amideimides, cyanate esters, and, more preferably, the
ethers, esters, sulfones, or imides. Generally, the hydrocarbons
are entirely aromatic with phenylene radicals between the linkages
that characterize the backbones. The oligomers can be linear or
multidimensional in their morphology. The components of these
coreactive blends should have overlapping melt and curing ranges so
that the crosslinking functionalities are activated at
substantially the same time, so that flow of the blend occurs
simultaneously, and so that, for heterocycles, the chain-extension
occurs in the melt where the products are soluble. Matching the
melt and curing ranges requires a selection of the chemistries for
the coreactive blend components, but achieving the match is readily
within the skill of the ordinary artisan.
The coreactive oligomer blends can comprise essentially any ratio
of the coreactive oligomers. Changing the ratio of ingredients, of
course, changes the physical properties in the final composites.
Curing the coreactive oligomers involves mutual (interlinking)
polymerization and addition polymerization. Therefore, we generally
use equimolar mixtures of the ingredients (i.e., the .xi. and Z*
components) in the blends.
The individual oligomers should initially have relatively low MW
(preferably no more than and, generally, around 10,000) and,
accordingly, should remain relatively easy to process until the
curing reaction when extended chain and block copolymers form to
produce the composite. A complex mixture of at least three types of
addition polymer form upon curing.
The coreactive oligomer blends can also include noncrosslinking
polymers, as desired, to provide the desired properties in the
composites. That is, the coreactive blend may include the two
crosslinking oligomers and a noncrosslinking compatible polymer,
thereby forming a blend with three or more resin components.
We can prepare oligomers of the general formula .xi.--R.sub.4
--.xi. or Z*.sub.k --B--Z*.sub.k by reacting suitable end cap
monomers with the monomer reactants that are commonly used to form
the desired backbones. For example, we prepare an imidesulfone as
we have already described by reacting a sulfone diamine with a
dianhydride. We prepare ethersulfones by reacting a suitable
dialcohol (i.e. diol, bisphenol, or dihydric phenol) with a
dihalogen as described in U.S. Pat. No. 4,414,269. Similarly, the
end cap monomers for the Z*.sub.k --B--Z*.sub.k oligomers generally
are selected from the group consisting of aminophenol, aminobenzoic
acid halide, H.sub.2 N--.O slashed.--SH, .O slashed.--W, or the
like, wherein W=--OH, --NH.sub.2, or --COX. The Z*.sub.k
--B--Z*.sub.k oligomers include any diamines, diols, or
disulfhydryls we have previously described- In this circumstance,
k=1.
Upon curing, the oligomers homopolymerize (i.e. addition
polymerize) by crosslinking and form block copolymers through the
Michaels addition reaction between the hydrocarbon unsaturation of
one oligomer and the amine, hydroxyl, or sulfhydryl group of the
other. The reaction of the hydrocarbon unsaturation of one oligomer
with the functionality of the other follows the mechanism described
in U.S. Pat. No. 4,719,283 to form a cydohexane linkage by bridging
across the double bond. With the acetylene (triple) unsaturation, a
cydohexene ring results.
The Michaels addition reaction is illustrated as follows:
##STR114## wherein V=--NH--, --O--, or --S--. For the other end
caps, we believe a reverse Diels-Alder decomposition reaction
(induced by heating the oligomers) results in the formation of a
reactive maleic moiety and the off-gassing of a cyclopentadiene.
The methylene bridge decomposes to the maleic compound at about
625-670.degree. F. (330-355.degree. C.) while the --O-- bridge
decomposes at the lower temperature of about 450.degree. F.
(230.degree. C.).
The reactive group might also be --CNO instead of the amine, but we
do not recommend use of these dicyanates.
While we have described preferred embodiments, those skilled in the
art will readily recognize alterations, variations, and
modifications which might be made without departing from the
inventive concept. Therefore, interpret the claims liberally with
the support of the full range of equivalents known to those of
ordinary skill based upon this description. The examples are given
to illustrate the invention and not intended to limit it.
Accordingly, limit the claims only as necessary in view of the
pertinent prior art.
* * * * *